A	B	C	D	E	F
G	H	I	J	K	L
M	N	O	P	Q	R
S	T	U	V	W	X
		Y	Z

Term	Definition
a-Particle	A particle of radiation that consists of two protons and two neutrons, and has an atomic charge of +2, and the at-rest mass of ~4 Daltons - a Helium-4 nucleus. Nearly all alpha particles are stopped by less than 10 cm of air, or the layer of dead skin cells on the human body.
b-Particle	A particle of radiation that is a high energy electron emitted by a neutron-rich nucleus. It has an atomic charge of -1, and the at-rest mass of 9.1091 × 10-28 grams. Nearly all beta particles are stopped by less than 10 layers of metal foil, or less than 2 cm of flesh.
g-Ray	A form of electromagnetic radiation emitted from a nucleus, or the disintegration of an electron-positron pair, that consists of a photon having the energy of 10 keV to 9 MeV. Gamma rays are very penetrating, and at least half will pass through a person without interacting with the atoms in the body. It takes nearly 30 cm of earth to reduce their level by half.
A
`A`a	(pronounced "ah-ah") A Hawaiian term for lava flows that have a rough, rubbelly surface composed of broken lava blocks called clinkers. See Pahoehoe for contrast. Images courtesy of U.S. Geological Survey.
Abutment	A mining term for, the base structure of an arch of rock spanning a passageway and supporting the weight of the rocks above passageway; and the solid rock ahead of the face and the settled packs behind the face, supporting the weight of the rocks over a longwall face.
Acicular	The mineral habit where the crystals are shaped like needles. Nearly all acicular crystals are prismatic. A good image example is Cuprosklodowskite.
Actinide Elements	A series of chemically similar radioactive elements having atomic numbers ranging from 89 through 103. The Actinide series of elements are: Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium In many ways similar to, and often considered to be a second series of, the Rare Earth Elements.
Active Workings	Any area in a mine where miners normally work or travel, and which are ventilated and inspected on a regular basis.
Adamantine	A surface luster characterized by being extremely flat, smooth and reflective, giving it the appearance of polished glass. Its appearance gives the mineral a visual 'feel' of being very hard, even if it isn't. An adamantine luster differs from a glassy luster by its extremely flat and smooth, almost jewel-like surface.
Adit	A passage driven into a mine from a hill or mountainside.
Aggregate	The mineral habit where the crystals are packed close together so they resemble grains, with the crystal structure not easily discernible. Compare with alluvial and glacial deposits. These deposits occasionally contain economically valuable minerals, such as tin, gold and platinum.
Alkali Earth	These are highly reactive metallic elements found in column IIa of the Periodic Table. They usually form alkaline cations having a valence of +2 in an aqueous solution. The following elements are the known alkaline metals: Beryllium Magnesium Calcium Strontium Barium Radium
Alkali Metal	These are highly reactive metallic elements found in column Ia of the Periodic Table. They form highly alkaline cations having a valence of +1 in an aqueous solution. The following elements are the known alkaline metals: Hydrogen † Lithium Sodium Potassium Rubidium Cesium Francium † Hydrogen is included in this column, but is usually not considered to be an alkaline metal.
Alluvial Deposit	A Sedementary deposit of minerals, usually sands and gravels, transported and deposited by the action of stream or river water.
Amorphous	Having no definable shape. Non-crystalline. Having no structure at the molecular level, such as glass or Obsidian. Not to be confused with anhedral.
amu	Atomic Mass Unit. See Dalton.
Andesite (ic)	A fine grained, dark colored, rock formed by extrusion. When it is an igneous rock, it contains phenocrysts, or small crystals, of zoned sodic plagioclase,primarily andesine feldspar, in a matrix of the same minerals as the phenocrysts. At least one of the mafic minerals is included. The term was coined by Bush in 1826 from the Andes Mountains of South America.
ANFO	A blasting agent used in quarrying made infamous by its misuse as an expedient terror explosive. It is a mixture of 23 kilograms of ammonium nitrate (NH4NO3) mixed with 19 liters of fuel oil (50 pounds of ammonium nitrate and 5 gallons of fuel oil). It has all but replaced dynamite as a non-permissible mining explosive (an explosive that produces considerable flame and toxic fumes, and thus is not permitted for underground use).
Ångström	(Symbol: Å). A unit of length equal to 10-10 meters. It is used to describe crystalline unit cell dimensions and the wavelengths of electromagnetic energy, such as visible light and x-rays. It is more properly termed 0.1 nanometer, but its long term and widespread usage has made 'Ångström' an acceptable unit of measurement, much like the barn is in nuclear cross section measurements.
Anhedral	Without form. An anhedral crystal is one that, for some reason, does not show its true form. A good example of this habit is Samarskite-(Y).
Anhydrous	Lacking any water.
Anion	A negatively charged ion that is attracted to the positively charged anode of an electrolyte cell. For example, the Carbonate ion ( CO3-2 ).
Aphanite	Synonymous with felsite, which see.
Atomic Mass	The mass of an atom, of a given isotope, of an element. It is expressed in Daltons. The average mass of the naturally occurring mixture of isotopes of that element, expressed in Daltons.
Atomic Mass Unit	See Dalton.
Atomic Number	The number of protons in the nucleus of each of the atoms of an element. This is a characteristic of that element.
Atomic Weight	See Atomic Mass.
Auger	A rotary drill used in mining and excavation that uses a screw-shaped device to penetrate, break up, and transport the drilled material.
Authigenic Mineral	A mineral formed from within a sedimentary deposit, and not carried into it.
Axis	A straight line of symmetry about which a body or geometric object rotates, or may be conceived to rotate.
Azimuth	A surveying term referring to the angle measured clockwise from any meridian (an established line of reference). See bearing.
B
Barn	(10-14 meter) A unit of linear measurement used in nuclear physics to describe the cross sectional area a nucleus presents to an incident particle for a stated interaction. The fission cross section presented to neutrons for Uranium-235 is sf = 580 ±2 barns.
Becquerel	Named for Henri Becquerel, who shared a Nobel Prize with Pierre and Marie Curie for their work in the discovery of radioactivity, it is one decay per second in a quantity of a radioisotope. It is sometimes used to indicate the quantity of radioisotope that, on average, will have one nuclear decay event each second.
Bench	A ledge created in an open pit mine or quarry. It forms the working surface for ore extraction. The size of the bench is dependent on the strength of the rock, stability of adjacent slopes, pit economics, and the machinery employed. One of two or more divisions of an ore deposit separated by waste rock, or formed by the process of mining.
Beneficiation	The treatment of mined material, making it more concentrated, or richer, by removing undesired material from the ore (i.e.: removal of ash, sulfur and pyrite from coal).
Bearing	Said of a mineral containing the material of economic interest. A surveying term used to designate direction. The bearing of a line is the horizontal angle between a line and the meridian (an established line of reference). Azimuths are angles measured clockwise from any meridian.
Birefringence	The effect of crystals of some minerals to have a different refractive index for light of different polarizations. This causes a doubling of an image viewed through the crystal. The most widely known such mineral is Calcite, seen with Uraninite images (007c) and (007d).
Bituminous Coal	Sometimes referred to as "soft coal," bituminous coal is a middle rank coal (between sub-bituminous and anthracite). It is formed by the action of additional pressure and heat on lignite. It usually has 11,500 Btu, or higher, heat value when burned.
Black Damp	A mining term for an oxygen depleted atmosphere, especially one that is a mixture of carbon dioxide (CO2) and nitrogen.
Black Light	Ultraviolet light; a lamp used to produce ultraviolet light
Blade(d)	The mineral habit where the crystals are shaped like long, thin, flat plates. Blade shaped crystals are similar to, but not, prismatic. Good examples are (1), (2), and (3) of Cuprosklodowskite.
Blasting	Pertaining to the use of explosives, particularly in mining or quarrying. Those involved or interested in blasting operations should obtain DuPont's Blasters' Handbook for a very educational description of the techniques for the safe use of explosives in mining and quarrying.
Blasting Agent	A low explosive (a low velocity explosive that heaves instead of shatters) consisting of a mixture of a fuel and an oxidizer (i.e.: ANFO - ammonium nitrate - fuel oil) used in mining and quarrying.
Blasting cap	See detonator.
Blasting Machine	A device designed to provide an electric pulse used to initiate electric detonators. They may be powered by battery, alternating current or human muscle power. The two most common are capacitive discharge and generator. The classic blasting machine is a large wooden box with a rack bar ("T"-handle) to which wires leading to the electric detonators are attached. The rack bar is pulled up, and then pushed down hard to generate the current used to set off the detonator(s).
Bloom	See efflorescence.
'Book'	See sphenoidal.
Borehole	Any deep or long drill-hole, usually associated with a diamond drill A hole drilled into rock to accept a charge of explosive that will be used to break up that rock. Empty boreholes may be used to buffer the surrounding rock to limit the extent of overbreakage, resulting in a gallery whose walls, roof and floor are of nearly intact rock.
Botryoid(al)	Shaped like a cluster of grapes. It is differentiated from radial clusters in that the ends of the radiating crystals form a generally smooth, or continuous, surface, and cannot be differentiated from each other. A fair example image of this is the Aragonite occurring with Blatonite.
Breccia	Broken rock held together by a clastic cement or fine grained material. From the Italian word for broken stones or rubble.
British Thermal Unit	The energy required to raise the temperature of one pound of water by one degree Fahrenheit, from 60° to 61°.
Brittle	A mineral is said to be brittle when it fractures at less than 3%-5% deformation or strain. Compare to ductile.
Btu	See British thermal unit.
By-product	Material of economic value produced by a process primarily intended to extract another material. For example palladium is produced as a by-product of platinum mining in South Africa.
C
Cation	A positively charged ion that is attracted to the negatively charged cathode of an electrolyte cell. For example, the Sodium ion ( Na+ ).
Cave	A deep hollow or natural passage under, or into, the earth that has one or more opens to the surface. It is usually to be passable by a human. Compare with vug.
Cavern	A large cave.
centiGray	(symbol: cGy) A radiation dose equal to one hundredth of a Gray. Directly equivalent to the obsolete radiation dose unit of one RAD for a dose of radiation.
centiSievert	(symbol: cSv) A radiation dose equal to one hundredth of a Sievert. Directly equivalent to the obsolete radiation dose rate unit of one RAD per hour for a dose rate for a radiation flux.
Clast	A clast is a particle or fragment of a rock or mineral that has separated from the parent body of that rock or mineral. Clast Sizes Particle Name Smallest Clast Size Description Boulders 256 mm Breccia (angular clasts) or Conglomerate (rounded clasts) Cobbles 64 mm Breccia (angular clasts) or Conglomerate (rounded clasts) Pebbles 4 mm Breccia (angular clasts) or Conglomerate (rounded clasts) Granules 2 mm Breccia (angular clasts) or Conglomerate (rounded clasts) Sand 1/16 mm Beach sand or sandstone Silt 1/264 mm Silt or siltstone (sometimes mudstone) Clay Less than 1/264 mm Shale (with bedding) or Claystone (without bedding) There are many causes for the break-up of rocks and minerals into clasts, both natural and human-caused. A few of these are: Natural Tectonic action Earthquakes (including tsunamis) Volcanic heating {expansion caused fracturing}; lava flows {mechanical movement}; ash {an abrasive} chemical action on existing, surrounding rock (carbon dioxide, water vapor, sulfur dioxide, hydrogen chloride, etc.) Weather Solar (diurnal heat and cold cycles) Rain caused leaching and mechanical washing Freezing (water expansion in cracks expanding those cracks until the rock's structure fails) Wind blown sand and dust Glacial ice grinding against rock structures deformation by weight and thrust Mechanical (one rock falling onto, or abrading, another) Biological bacterial etching plant growth animal activities (including waste break-down and carbon dioxide combing with rain water) its presence/absence modifying weather (deserts to rain forests) Humans interacting with our surroundings Construction (buildings, roads, dams, bridges, etc.) Transportation (off road vehicles, hiking, etc.) Farming (both physical and chemical effects) Mining (both physical and chemical effects) Modification of natural processes pollution (chemicals reacting with rocks, acid rain) weather pattern modification changes in the biosphere
Clastic	Pertaining to rock or sediment composed of fragments and material derived from other rock, transported and deposited to form new rock. For example, sandstone and shale.
Cleavage	Plane(s) of breakage through a crystal that results in a smooth, even break.
Cloudy	Having a diaphaneity that is somewhat less than fully transparent, as if containing a light fog.
Cluster	A group of crystals showing an underlying order in their placement. This order may be either two- or three-dimensional. An example of a two-dimensional cluster is Haynesite, and an example of a three-dimensional cluster is Kasolite on Cuprosklodowskite.
Colloform	Formed of ultra-fine grained particles into a reniform or botryoidal shape. It is usually finely banded from variations in the content of the suspended material forming it. From collo- for colloid, which these deposits were once believed to have been formed from.
Concentrate	Material that has been enriched in the desired mineral by removing undesired waste rock.
Concentration/ing	The process of separating milled ore into two streams; one greatly enriched in the desired mineral (concentrate) and the other of waste material (tailings). Concentration is an economically vital step in the production process because it reduces the volume of material which must be transported to, and processed in, a smelter and refinery, as well as reducing the toxic waste often generated by refining.
Conchoidal	Fracturing with a resultant surface characterized by smooth, shell-like convexities and concavities, as on fractured obsidian or glass. A good example of this habit is Samarskite-(Y). Taken from the word conch, for shell, which this fracture resembles.
Corundum	A mineral whose primary chemical component is alumina, chemically aluminum oxide ( Al2O3 ). The two best known varieties of this mineral are Ruby (contains a trace amount of chromium oxide) and blue Sapphire. Corundum is often synthesized and used as an abrasive.
Crevice	A long, narrow crack in a rock.
Crust(s)	A hard, crisp covering coating formed on the surface of rock by the drying of a solution of the mineral. An example is Andersonite. See efflorescence.
Crystal	A homogenous solid formed by a repeating, three-dimensional pattern of atoms called a Unit Cell, ions, or molecules, and having fixed distances between constituent parts, and is usually characterized by external planar faces.
Crystalline	Relating to crystals. Having a regular pattern or structure at the molecular level, but without necessarily showing crystal form at the visible level.
Curie	Named for Marie and Pierre Curie, this is an obsolescent term for 3.7 × 1010 Becquerels, or nuclear decays per second. It is also approximately the number of Becquerels for 1 gram of Radium-226.
Current Ripple Mark	Ridges, usually of sand, caused by the flow of water. The ridges are perpendicular to the direction of flow, and are generally parallel, equally spaced apart and of the same size. Most often seen on river beds or at the bottom of lakes or the sea. Two examples (#1) (#2) of current ripple marks formed from deposited aragonite can be seen in this image of Blatonite.
D
Dalton	(Symbol: u) A unit of Atomic Mass, equal to 1/12th the mass of one electrically neutral, unexcited, atom of Carbon-12 (1.6604 × 10-24 grams). Used to express the mass of a single atom or molecule.
Daughter	An element/isotope resulting from the radioactive decay of a parent element/isotope. For example, Thorium-234 is the daughter resulting from the a-particle radioactive decay of Uranium-238.
Decline	An inclined shaft within an underground mine used to transport workers, materials and ore to and from the working stope in a mine.
Dense Media Separation	A pre-concentration process, used by some high value minerals refineries, which separates relatively light and heavy particles by immersion in a liquid of an intermediate density. The denser materials sink, while the less dense materials float to the surface and are skimmed off. The desired fraction is further processed and concentrated. As the floatation liquid is usually not water (see Froth Flotation), it can be expensive, and therefore is usually only used for high value minerals extraction.
Density	See Specific Gravity.
Detonator	A small device used to initiate a detonation wave in an explosive. Non-electric detonators are initiated by crimping a fuse into their open top. When the fuse burns down to the layer of first-fire compound in the detonator, this layer deflagrates and sets off the primary explosive. This primary explosive, originally mercury fulminate but today lead azide, detonates and creates hot spots withing the main charge of the explosive, which in turn transition into a detonation wave. For less senitive explosives, such as TNT, the detonator may have a booster charge of a more stable, but easily initiated, explosive, such as PETN. An electric detonator replaces the fuse with an electric bridge wire to initiate the first-fire compound. Today, less sensitive detonators have been developed. To eliminate the somewhat variable time delay, sesmic detonators were developed for oil exploration. These used a thin bridge wire next to the primary explosive in the detonator. A high volotage, high current is dumped into the bridge wire, causing it to detonate. The exploding bridge wire detonator evolved into the slapper detonator. The exploding bridge wire punches out and accellerates a disk of aluminum foil. The gasseous vapor of the exploded bridge wire accellerates this disk down the central tube in an aluminum cylinder. At the end of the cylinder is a pellet of PETN. The impact of the aluminum foil disk into the PETN initiates it into detonation. These last two detonators were developed for use in nuclear weapons, where the elimination of all primary explosives is desired to reduce the potential of a detonation during an accident, with the subsequent scattering of nuclear material. Implosion nuclear weapons require precise timing of all their detonators to acheive a nuclear detonation. Together with the use of explosives, such as TATB - an extremely stable explosive that does not degrade after 24 hours at temperatures that will melt solder, nuclear weapons have become quite resistant to accidental initiation of their high explosives.
Detritus	Very small, loose fragments of rock caused by weathering, mechanical breakage or blasting of rock and mineral masses.
Diaphaneity	The degree of transparency, or ability to pass light, without interfering with that passage.
Dichroism	The property of some crystals to show two different colors when viewed along different axes. An example of dichroism is Masuyite, which shifts from a wine red (001) to a more crimson red (100). Also see pleochroism.
Disseminated	An ore whose deposits consist of fine grains of ore mineral dispersed through the host rock. An example of this is black grains of Coffinite dispersed through sandstone.
Druse	A crust of tiny crystals coating a rock, or lining a cavity, usually composed of the same mineral(s) of that of the rock.
Ductile	Easily deformed. A mineral is said to be ductile if it able to be deformed 5%-10% without fracture of faulting. Compare to brittle.
E
Earthy	Having a non-reflective, dull appearance resembling earth or clay.
Efflorescence	The growth of mineral crystals or crusts on the surface of rock in a mine, or elsewhere, caused by the evaporation of the water which that mineral is dissolved in. Often called "bloom".
Effusive	See extruded.
Ejecta	Material blown out of a volcano during an eruption. Specimen #1 of Piergorite is such material.
Electron Volt	The energy acquired by an electron when it is accelerated through an electrical field gradient of one volt (approximately 1.602 × 10-19 joule). Used as an expression of energy possessed by atomic and sub-atomic particles, and electromagnetic radiation.
Element	A group of atoms characterized by having the same number of protons in their nucleus, and thus, the same electron shell structure. They cannot be transmuted into other elements except by nuclear means, such as the capture of electrons, protons, a-particles. Neutron capture does not change the element, but may the subsequent emission of a-particles, b-particles or fission, which does. Their chemical and physical properties vary only extremely slightly from each other due to differing numbers of neutrons in their nucleus. The nuclear properties will vary quite markedly with the different numbers of neutrons they possess.
eV	see electron volt.
Euhedral	Showing no outward crystal form. The growth of the crystal was bounded by contact with neighboring crystal growth, preventing the crystal faces from showing. The faces present by the grain are referred to as rational faces. Grains of amorphous minerals, such as Obsidian, are not referred to as being euhedral.
Explosive	Any substance that can be caused to release energy and increase its volume in milliseconds or less. The energy released during this process can be used to break rock. Nuclear explosives have not found any practical use as mining explosives due to their cost, magnitude of yield, and radioactive residue.
Extrusive	A term used to describe igneous rock that has been erupted onto the earth's surface.
F
Facet(s)	The plane surface(s) shown by a crystal.
Feldspar	A group of igneous rock-forming minerals having the general formula of 'X'Al(Al, Si)3O8, where 'X' can be: Potassium (K); Sodium (Na); Calcium (Ca); Barium (Ba); Rubidium (Rb); Strontium (Sr); or Iron (Fe). Feldspars are white to gray to pink in color, with a Mohs' hardness of 6. They are monoclinic or triclinic in symmetry, and often twinned. Feldspars comprise 60% of the crust of the earth. They are therefore the most common and widespread group of minerals to be found on earth. Their most common use is for road paving and as fill stone for concrete.
Feldspathoid	A group of uncommon rock-forming minerals, related to feldspar, only containing less silica in their make-up. They take the place of feldspars in igneous rocks that are silica deficient. They never occur in the same rock with quartz. They are sometimes referred to as foid or lenad.
Felsic	A light colored igneous rocks. The term is a mnemonic for its feldspar, lenad (feldspathoid), and silica content. It may or may not contain phenocrysts. It is the complement of mafic. Also see Felsite.
Felsite	Synonymous with Aphanite. Any porphyritic igneous rocks characterized by its light color and very fine grain. It may occasionally contain phenocrysts (isolated, barely visible crystals). They differ from other porphyitic minerals by their light color.
Fibrous	Appearing to be composed of many long, thin, generally straight acicular rods. An example is Piergorite.
Fluorescence	The emission of visible light under the stimulation of a substance by the absorption of incident radiation (in mineralogy, this is taken to be ultraviolet light), and persisting only as long as the stimulation is continued. Compare to phosphorescence. The ability to, and color of, fluoresce under ultraviolet light is often used as an indicator in the identification of minerals. It is, however, less than reliable as it is too often dependent on the presence of activators - elements that assist in fluorescence - and the absence of 'poisons' - elements that inhibit fluorescence. Very often, an activator must be present above a certain percentage to be effective, but be less than another quantity or it becomes a 'poison' to fluorescence. These activators may be absent at the location of some deposits of the mineral, making it non-fluorescent. In addition, the type of activators, and the presence of certain modifiers, can alter the color of the fluorescence. To further complicate the use of fluorescence in identifying minerals, some minerals can fluoresce so strongly that it can be easily seen in ordinary or even sunlight (an example is Andersonite - Compare to ordinary light only).
Foid	See feldspathoid.
Foliate	Formed as, or able to split into, thin leaf like layers, or folia. Usually taken to mean coarser layers than a micaceous mineral
Fracture	The process of breaking.
Froth Flotation	A method of mineral concentration which separates the various minerals in the raw ore feed from each other by using the differing surface properties of the minerals. The Separation is achieved by passing air bubbles through the mineral pulp, a water slurry of pulverized ore. By adjusting the chemistry of the pulp, using various reagents, the desired minerals can be made aerophilic (air attracted, wettable) and gangue minerals aerophobic (water avoiding). Separation occurs by the desired minerals adhering to the air-bubbles, which form an easily separated froth floating on the surface of the pulp.
Fumarole	A vent hole in a volcanic area from which hot smoke and gases escape, and around which some minerals, such as sulfur as in the above linked image, may condense. Image courtesy of the U.S. Geological Survey.
G
Gangue	Material in the ore of no economic value. Waste rock that is placed in the mine tailings dump.
Geiger-Mueller Counter	An electronic instrument used for detecting and measuring low level b-particle and g-ray radiation. The tutorial on the Geiger-Mueller Counter is recommended.
Geode	A nodule, usually greater than 2 cm in diameter, consisting of primarily one or more Quartz minerals. Most are solid, consisting of multicolored layers of Chalcedony. Many are hollow, containing a lining of Quartz crystals. For this reason, they are often cut in half to expose their internal esthetic structure. See vug for comparison.
Geothermal	Heating due to the increasingly high temperatures that occur as the depth below surface level increases. Geothermally heated water is responsible for geysers and other hydrothermal processes,
Geyser	A natural hot spring that intermittently ejects a column of water and steam into the air. This is the most commonly seen hydrothermal process.
Glacier	A 'river' of accumulated of snow, compacted by gravity and weather into ice, often found on the upper slopes of mountains. There movement is extremely slow, usually measured in centimeters, or meters, per day.
Glass	Referred to minerals that are amorphous, having no structure at the molecular level.
Glassy	See Vitreous.
G-M Counter	See Geiger-Mueller Counter.
Gneiss	Gneiss is a high grade metamorphic rock that has been subjected to more heat and pressure than schist. It is coarser than schist and has distinct alternating banding of feldspar (primary mineral), mica, quartz, hornblende, muscovite, biotite and garnet. Gneiss can be formed from sedimentary rock (i.e.: sandstone or shale), or from the metamorphism of the igneous rock (granite).
Grade	The concentration of desired metal(s) in a given mass of ore. Grades are normally expressed grams per tonne, equivalent to parts per million. For high concentration ores, this may be expressed as kilograms per tonne. An inclined slope. The degree of an inclined slope, expressed as a percentage. The percentage is found by dividing the change in altitude by the horizontal distance traveled. A 45° incline changes 1 meter in height for every meter of lateral travel, thus it is a 100% slope. A 13% slope changes 13 meters in height for every 100 meters of horizontal travel, or declines 4.41° from the horizontal.
Grain	A particle of rock or mineral under a few millimeters in diameter.
Gravel	See clast.
Gray	(symbol: Gy) The Gray is the S.I. standard unit of measure for radiation exposure. It is the quantity of radiation that will deposit 1 joule of energy into 1 kilogram of the target material. The Gray is the dose of radiation received, not the rate at which it is received. (see also Sievert). To make it conform to the older standards of radiation dose measurements, the centiGray is usually used, as 1 centiGray = 1 RAD of radiation exposure.
Greisen	A modified granitic rock whose chief components are roughly equal parts of quartz, perthitic alkali feldspar and plagioclase feldspar, and small quantities of biotite mica.
Groundmass	The mineral between phenocrysts in igneous porphyritic rock. Synonymous with matrix.
Grus	Sharp, course grained fragments from the disintegration if crystalline rock, particularly granite, and usually in arid or semi-arid areas.
Gy	See Gray
H
Habit	The preferred crystal and general appearance of a mineral, the common way it is found in nature. This is not to be mistaken for the mineral's crystallographic form.
Half-Life	The time required for one half of a quantity of a specific radioactive isotope of an element to decay by the emission of a radiation particle (a-particle or b-particle) or electromagnetic radiation (a-ray) into another form. The daughter of this radioactive decay may or may not also be radioactive.
Halogen     (Halide)	A family of highly reactive non-metallic elements that can accept a single electron from a donor atom. These elements are: Element Symbol Atomic Number Atomic Mass (common) Fluorine F 9 18.998403 Chlorine Cl 17 35.453 Bromine Br 35 79.904 Iodine I 53 126.9045 Astatine † At 85 209.987 † t1/2 = 8.1 hours
Hardness	See Mohs' Hardness.
Head Grade	Also called mill head grade. The grade of the ore leaving the mine and entering the processing plant. It also refers to the grade of ore as it enters the milling process.
Host Rock	A mineral, usually the majority mineral of a specimen, which supports a mineral of interest, but does not come in contact with that mineral. A substrate mineral separates the mineral of interest from the host rock's mineral(s). Compare to matrix and substrate rocks.
Hot Radicals Theory	See Theory of Hot Radicals.
HREE	Abbreviation for Heavy Rare Earth Elements.
Hyaline	Transparent, clear, glass like. See diaphaneity.
Hydrate	A chemical compound that has one, or more, water molecules added to its composition. The addition is through hydrogen bonding, and not chemical reaction, such as ionic bonding, into the molecule. The water is an integral part of the crystal structure, and thus part of its chemical composition. An example of this is Uranophane (Ca(UO2)2Si2O7 · 6H2O), which has six water molecules added to it through hydrogen bonding, indicated by the elevated dot between the base molecule of Uranophane and its added water.
Hydrocarbon	A family of chemical compounds containing only carbon and hydrogen atoms in various combinations, other than rings. They are found in fossil fuels, such as petroleum or crude oil.
Hydrolith	From hydro, for water, and lith for stone. A mineral that is precipitated from water by chemical action. A rock that has little or no organic matter. A sedimentary rock consisting of carbonate particles (i.e.: Limestone).
Hydrothermal	From hydro for water, and thermal for heat. Used to indicate that a process, such as mineral formation, is the result of the action of hot water. The most common cause of hydrothermal processes is geothermal heating of underground water.
Hygroscopic	Readily absorbing water, especially from the air.
I
Igneous	From the Latin word igneus, for Fire. A term used to designate minerals , rock or geology formed by magma or lava.
Igneous Rock	Rock formed from the solidification of magma or lava. From the Latin word igneus, for Fire.
IMA	The International Mineralogy Association
Inby	A mining term used to indicate in the direction of, or by, the working face.
Index of Refraction, or, Refractive Index	The ratio between the velocity of light in a vacuum to that in a given material: n   =   c/v where: c   =   Velocity of light in a vacuum           (2.99792458 × 1008 meters per second); v   =   Phase velocity of light in the medium under consideration           (essentially, the apparent velocity). At the junction between two transparent media, this causes a change in the direction of the ray of light, called refraction. This effect is made use of in lenses for microscopes and telescopes. When the index of refraction in a crystal differs for different polarizations of light, a doubling of an image seen through the medium may be seen. This is termed birefringence, which see for examples.
Insosilicate	See Silicate.
International Mineralogy Association, The	The International Mineralogy Association is the organization which maintains a public listing of all the approved mineral names, by its Commission on New Minerals and Mineral Names (CNMMN), for all minerals since 1959 for which official determinations are on record. The official designations are: (A) approved, (D) discredited, and/or (R) for redefined. Mineral names missing from this list are those species that were grandfathered (GP) as being valid prior to 1959.
Ion	An atom, or group of atoms, that have acquired a net electric charge by the gain or loss of one or more electrons.
Iridescence	Have the property of causing reflected light to show a 'play' of several colors across the mineral's surface.
Isotope	Atoms of an element having the same number of protons (atomic number), but different numbers of neutrons. This results in different atomic masses between two isotopes of the same element. Isotopes have very similar chemical and gross physical properties, but greatly different nuclear properties. An example is the difference between Uranium-235 and Uranium-238.
J
Jackleg	A percussion drill used in mining, usually pneumatically powered, mounted on a telescopic support leg that can extend to about 2.5 meters. The leg and drilling machine are hinged so the drill need not be in line with the leg. It is used for drilling boreholes in a rock face.
joule	(Symbol = J) The unit of energy equal to the work done when a force of 1 Newton acts through a distance of 1 meter. It is also the energy from one Ampere of electricity passing through 1 ohm for a period of time of 1 second.
K
keV	Kilo (thousand) Electron Volts. See electron volt.
kilogram	The mass of the International Prototype Kilogram, or IPL, located in Paris, France, and is the standard mass for the International System of Measurements, S.I. Due to the varriability of the secondary standards, and no attempt to verify if the primary standard is also varrying agains a physical constant of the universe, there is a move to redefine the kilogram away from an artifact and to a physical constant of the universe. All of the other primary physical constants have been so redefined. The kilogram is the only primary standard unit of measure to use 'kilo' in its name. However, in keeping with the standards of usage for scaling prefixes, the prefixes are used with the gram and not the kilogram. Thus, milligram and not microkilogram.
L
Lahar	An Indonesian word for a landslide or rapidly moving mudflow, or the deposit left by one, of volcanic ash and fragments mixed with water. It occurs on the flanks of a volcano, or the stream beds and channels below it. Image courtesy of the U.S. Geological Survey.
Lamprophyre	A group of dark minerals occurring in volcanic dikes as either phenocrysts or the groundmass. They readily weather to light colored minerals. Constituent minerals are: biotite, hornblende, pyroxene, and feldspar or feldspathoids. Commonly associated with carbonates.
Lava	Magma (molten rock) that reaches the earth's surface through a volcano or fissure. From the Italian word for stream. The igneous rock formed by the cooling and solidifying of molten rock on the earth's surface. Image courtesy of U.S. Geological Survey.
Lava Coil	See Pahoehoe lava coil.
Lenad	See feldspathoid.
LHD Vehicles	(Load-Haul-Dump Vehicles) - Mine vehicles, used in some underground mines, to transport ore from the working areas to the main haulage system.
LREE	Abbreviation for Light Rare Earth Elements.
Luster	The surface appearance of a mineral.
M
Mafic	A term used for an igneous rock whose composition is mainly dark, iron-magnesium rich minerals (e.g.: biotite, hornblende, and pyroxene). It is also used as a descriptive for those minerals. It is a term derived from magnesium + ferro + ic.
Magma	The molten rock material under the earth's crust, from which igneous rock is formed by cooling. See Lava.
Massif	A large mountain, or group of connected mountains, that are a part of, but independent from, a mountain range.
Massive	The state of a mineral where its crystals are so intergrown that their crystalline form is not discernable.
Matrix	A mineral within, or upon, which another mineral occurs. Synonymous with groundmass.
Meridian	A surveying term for an established line of reference. The bearing, or azimuth, is the designate direction measured clockwise from the meridian.
Metacryst	A large crystal developed in metamorphic rock by recrystallization from another mineral. For example, Garnet and Staurolite from recrystallization in mica schist.
Metamict	The disruption of the crystalline structure at the atomic level by radiation, yet retaining the original macroscopic crystal form or shape. This is common among radioactive minerals, and those minerals that are found close to them. The cause for uranium and thorium minerals becoming metamict is not the g-ray radiation, but is instead the a-particles that they, and their daughters, emit. a-particles, being very massive and highly charged, deposit their energy within a small fraction of a millimeter from where they were emitted within the mineral, causing massive local disruption of the crystalline matrix. Over time, this will cause the crystal structure, at the atomic level, to be disrupted. While g-rays do contribute to this disruption, it is only a minor contribution due to their being so penetrating that most escape the mineral's mass.
Metamorphic	A mineral that has been changed from another mineral by the action of pressure and/or heat. It can also occur by the chemical action, solution or dissolving of some component part of the mineral (see metasomatism).
Metasomatism	The alteration of the chemical composition of a rock or mineral by interaction with dissolved chemicals and gases in capillary fluid. This causes the mineral to be changed into another mineral without melting, and usually with little or no change in volume or shape.
Meteoric	Falling from the sky. Usually meaning meteors (rocks from space); rain.
Methane	(Chemical formula: CH4). A gas formed naturally from the decay of vegetative matter that, when mixed with approximately 9 parts air, becomes explosive. Methane, the principal component of natural gas, is frequently encountered in underground coal mining operations. It is kept within safe limits through the use of extensive mine ventilation systems.
MeV	Mega (million) Electron Volts. See electron volt.
Miarolitic	Said of igneous rock that has many small, irregular cavities. These cavities are usually more angular and irregular than those of a vug. An example is the coarse grained granite host of the mineral Ulrichite.
Micaceous	Having the character of splitting into very thin, flexible sheets.
Microcrystal	Crystals of less than 0.01 millimeters in their greatest dimension. These crystals, usually occurring in masses, are so small that only their speckle reflections are all that betray their existence at 30X magnification. A good example of microcrystals is Vanuralite.
Microphotograph	A miniaturized photograph. The best know are microfilm used to store documents, and microdots used by spies. Compare to photomicrograph.
microSievert	(symbol: mSv) A radiation dose rate equal to one millionth of a Sievert. It is equivalent to the obsolete radiation dose rate unit of 0.1 milliRAD per hour for a dose rate for a radiation flux.
Milling	The first stage of mineral processing in which the ore pieces from the mine are further mechanically reduced in size to maximize efficiency of the concentration process. In general, two types of mills are used: autogenous mills simply tumble the ore to achieve the desired grain size; while other mills use an additional media, such as steel balls or rods, to aid milling.
milliRAD	One thousandth of a RAD.
Mimetic Twins	Pseudo-symmetry caused by twinning of two (2) or more crystals. Two good examples, (Image #1 and Image #2), are the crystal twins of Kobeite-(Y) from Kobe, Japan. (Crystals of this mineral from Hiroshima city, Japan, do not show this twinning).
Mine	An excavation in the earth from which ore or minerals can be extracted. These may be primarily on the surface or underground.
Mineral	A naturally occurring, homogeneous solid inorganic substance having a definite chemical composition and physical properties, such as a characteristic crystalline form, color, and hardness.
Mohs' Hardness	A relative system of scratch hardness used for classifying minerals. It uses a set of well known and defined minerals of relatively common occurrence as its standards of hardness. A mineral that will scratch another mineral, but cannot be scratched by it, is harder than that mineral, and will have a higher Mohs' number than it. If a mineral that will not scratch another mineral, but can be scratched by it, is softer than that mineral, and will have a lower Mohs' number than it. If a mineral that will scratch another mineral, and can be scratched by it in return, they are both the same hardness, and will both have the same Mohs' number. Mohs' Scale Mohs' Number Mineral Brinell Hardness 10 Diamond - 9 Corundum 667 8 Topaz 304 7 Quartz 178 6 Feldspar 147 5 Apatite 137 4 Fluorspar 64 3 Calcite 53 2 Gypsum 12 1 Talc 3 As can be seen, the Mohs' hardness is not directly related to a mineral's true, Brinell, hardness. Also, the crystal face being tested may affect the hardness, some faces showing a harder surface than others. In addition, the conditions during, and subsequent to, formation can have a small effect on a mineral's hardness. This is why many minerals are given a range of hardness.
Molecule	A molecule consists of two or more atoms chemically bonded together. It is the smallest particle, composed of two or more similar or different atoms, into which an element or a compound can be divided down to without changing its chemical and physical properties.
Monoclinic	A crystal form having three unequal axes, two of which intersect obliquely and are perpendicular to the third. The longest axis between two parallel faces is the [100] axis.
Mother Liquor	The solution of anions and cations that form the source of materials for the formation of crystals. The growth medium for crystals.
N
Nacreous	Pearly luster, like that of mother-of-pearl.
Nepheline	A Feldspar mineral, common worldwide, that consists of sodium-aluminum silicate and/or potassium-aluminum silicate. It occurs in igneous rocks and used in the manufacture of ceramics and enamels From Greek word for cloud, nephele, because its fragments become cloudy when placed in nitric acid.
Nodule	A small rounded mass of mineral, or mixture of minerals. It is visually different from the surrounding rock or sediment, and is often harder, causing it to weather out as a separate entity. See geode for comparison.
Nucleus	Center. The center of a mass, often the 'seed' on which the mass formed. Natural pearls often have a sand particle nucleus on which the pearlite was deposited by the oyster. The center of an atom composed of protons (which give it its' positive charge) and, with the exception of Hydrogen-1, neutron(s), and contains the majority of the atom's mass.
O
Oblast	An administrative territorial division within a constituent republic of Russia or the former Soviet Union.
Oolitic	Forming spheres between 1 and 2 mm in diameter.
Opaque	Diaphaneity that is the total exclusion of transmitted light. Impenetrable by light.
Open Pit Mine	A mine or quarry based on ore extraction from a surface excavation, which remains open to the surface for the life of the mine.
Ore	Rock from which economically important metal(s) or mineral(s) (i.e.: iron and diamonds) can be extracted.
Ore mineral	A mineral which contains a metal(s) which can be extracted at a financial profit.
Orthorhombic	A crystalline form consisting of three mutually perpendicular axes, all of different length.
Overbreakage	A mining and quarrying term for the breaking of the rock beyond the desired limits during blasting. To limit overbreakage, a line of boreholes, with no explosives loaded into them, are drilled to form a shear plane to limit breakage beyond this plane.
Overburden	The rock and/or earth, of little or no economic value, overlaying an ore deposit.
P
Pahoehoe	Pahoehoe is a Hawaiian term for basaltic lava that has a smooth, hummocky, or ropy surface. A pahoehoe flow typically advances as a series of small lobes and toes that continually break out from a cooled crust. See A'a' for contrast. Image courtesy of the U.S. Geological Survey.
Pahoehoe lava coil	These are spiral or scroll-shaped features that form along slow-moving shear zones in a Pahoehoe lava flow; for example, along the margins of a small channel. The direction of flow can be determined from a lava coil. Lava on the right side of the photo was moving toward the top of the view relative to lava on the left side. Images courtesy of the U.S. Geological Survey.
Pearly	A smooth, shiny, luster resembling pearls or the 'mother of pearl' found in sea shells. An example of pearly luster is Schmitterite.
Pedial	In the Triclinic system, a crystal form having no symmetry. Rarely seen in nature.
Pegmatite	A coarse-grained granite, sometimes rich in rare elements such as uranium, tungsten, and tantalum.
Periodic Table of the Elements	A table listing of the elements according to their atomic numbers, arranged so that those elements having similar chemical properties are in the same column.
Perthitic	The separation of one mineral from another by solid precipitation, forming a lattice type intergrowth, usually as thin, roughly parallel, layers in a host crystal.
Petrified Wood	Wood that has had its organic components (i.e.: cellulose, lignin, etc.) replaced, most commonly, by calcium carbonate, silica or uranium oxide. In uranium oxide petrified wood, the mineral Uraninite is formed. It is believed that the decaying wood results in a chemically reducing zone being produced, converting the U6+ into the less soluble U4+, which precipitates out as Uraninite, replacing the wood's organic structure.
PGE	Platinum Group Elements. See Platinum Group Metals.
PGM	Platinum Group Metals.
Phenocryst	A relatively large or conspicuous, ordinary, crystal formed during the early generation of porphyritic rock. In absolute terms, these crystals are usually still quite small.
Phosphorescence	The persistent emission of visible light following exposure to, and removal of, incident radiation (in mineralogy, this is taken to be ultraviolet light) - compare to fluorescence.
Photomicrograph	A photograph taken through a microscope. Compare to microphotograph.
Piezoelectric	Having the property of certain crystals of generating an electric charge when placed under mechanical stress, or of being deformed when an electrical charge is placed across it. See triboelectric for comparison.
Pinacoid	Also: Pinacoidal. A Triclinic form having only two (2) parallel faces that are considerably more prominent than any other face. No two other faces are parallel.
Pisolitic	Forming spheres between 2 and 10 mm in diameter, such as Bauxite.
Placer	An alluvial or glacial deposit where heavier minerals (such as gold and platinum) are deposited in the lower layers.
Plagioclase	A group of triclinic feldspars that are among the most commonly encountered minerals. They are formed at high temperature (igneous rock) and have the general composition (Na,Ca)Al(Si,Al)Si2O8. It is a mixture of oxides, silicates and aluminates in solid solution, forming a series of minerals composed of various ratios of the sub-groups Ab = [NaAlSi3O8] and An = [CaAl2Si2O8]. The series of minerals are: albite Ab = 100% - 90% An = 0% - 10% oligoclase Ab = 90% - 70% An = 10% - 30% andesine Ab = 70% - 50% An = 30% - 50% labradorite Ab = 50% - 30% An = 50% - 70% bytownite Ab = 30% - 10% An = 70% - 90% anorthite Ab = 10% - 0% An = 90% - 100% The term is sometimes used interchangeably to mean one of these minerals.
Planck's Constant	(Symbol = h) Planck's Constant = 6.62608 × 10-34 joule-seconds. The energy (E) of a photon is found from its' momentum (p), frequency (v) and the speed of light (c) or its' wavelength (l): E   =   p/c   =   hv/c   =   h/l It is used in calculating the energy of an electromagnetic photon.
Plate	A smooth, flat, relatively thin, rigid form of uniform thickness, usually coarser than Micaceous.
Platinum Group Elements	See Platinum Group Metals.
Platinum Group Metals	(Abbreviated PGM) The six metallic elements platinum, palladium, rhodium, ruthenium, iridium and osmium. Platinum occurs as either in placer deposits, or in host mineral deposits. These are two images of a placer platinum nugget (example #1 - front, example #1 - back), and twinned platinum crystals that was extracted from its rock matrix. Other PGM's are often alloyed with platinum. Gold, seen on the crystals, is a common deposit on platinum crystals.
Pleochroism	The property of some crystals to show different colors when viewed along different axes. This is given for the colors seen along three different axes. An example of pleochroism is Schröckingerite. Another example is Astrocyanite. Also see dichroism.
Pluton	A body of igneous rock formed beneath the surface of the earth by consolidation of magma. A mass of molten magma that, when it forces its way to the surface, results in a volcanic eruption.
Polarization	The orientation of the electric field component of an electro-magnetic wave relative to the direction of propagation of that wave. This term is most often used, mineralogically, for the birefringence of certain minerals, and the light used to examine thin sections of minerals.
Porphyr(y)(itic)	Any of a group of igneous rocks that is characterized by extremely fine grain and which may contain phenocrysts.
Prism	A solid figure whose opposite faces have the same size and shape and are parallel to one another. Each of the faces of a prism is in the form of a parallelogram.
Prismatic	The mineral habit where the crystal form whose opposite faces have the same size and shape and are parallel to one another. Each of the faces of a prism is in the form of a parallelogram. Acicular prisms are very long and narrow, while the prismatic habit is much thicker.
Propylite	An andesitic igneous rock, formed by hydrothermal alteration, which resembles greenstone. It contains minerals such as calcite, epidote, serpentine, quartz, pyrite, and iron oxides.
Proton	The positively charged particle found within the nucleus of an atom, and is the nucleus of Hydrogen-1. The number of protons in the nucleus determines the atomic number, and thus the element, to which that atom belongs. It mass is ~1836 times the mass of the electron, its negatively charged counterpart. Its physical properties are: Mass: 1.673 × 10-24 grams Radius: ~10-15 meters Charge: 1.602 × 10-19 coulombs Spin: 1/2 h       (h = Planck's constant / 2p) Magnetic Dipole Moment: 1.411 × 10-26 joule/tesla
Pseudomorph	A mineral showing the crystal form of another mineral rather than that its own characteristic form. This is often due to either the original mineral's chemical make-up changing to that of the current mineral, or the current mineral depositing into a hollow mold of the original crystal after it has eroded away.
Pyroclastic Flow	A ground-hugging avalanche of ash, pumice, rock fragments, and volcanic gases, traveling down the side of a volcano at 100 km/hour, or faster. It can have a temperature greater than 500° C. When it comes to a rest, its component solids may compact, deform (flatten) and weld together due to its intense heat and weight. A pyroclastic flow is believed to have buried Pompeii during an eruption of Mount Vesuvius in A.D. 79. The city was rediscovered in 1748. Image courtesy of the U.S. Geological Survey.
Q
Quarry	An open excavation, or pit, from which rock and stone, as opposed to a mineral ore, is obtained by digging, cutting, or blasting.
R
RAD	(obsolete) Radiation Absorbed Dose. A unit of energy absorbed from ionizing radiation, equal to 100 ergs per gram, or 0.01 joule per kilogram, of irradiated material. A whole body dose of gamma radiation of 500 RADs is considered to be lethal to at least 95% of the human population. The standard unit of radiation dose under the S.I. international standard units of measurement is the Gray. 1 RAD = 1 centiGray.
RAD per hour	(obsolete) The radiation dose rate that causes the absorption of one (1) RAD in one (1) hour of time. The standard unit of radiation dose rate under the S.I. international standard units of measurement is the Sievert. 1 RAD/hour = 1 centiSievert.
Radial Cluster	A group of prismatic or acicular crystals that appear to be growing from a single point. It is one form of the spherulite habit. This form differs from botryoidal clusters in that the individual crystal ends are easily discernible, instead of forming a continuous surface. A good example image of this is Ulrichite. Another excellent example image of this habit is Haiweeite.
Radiation	Subatomic particles (a-particles and b-particles), or high energy photons (g-rays), emitted by a radioactive substance, such as Uranium or Thorium. Radiation is impossible to avoid as its sources are everywhere around us. The average resident of the United States receives approximately 5 centiGray of radiation each year, over half of which comes from nature. The average airplane flight, at cruising altitude, will result in approximately ten microGrays radiation dose per hour of flight. Unless one visits a nuclear facility or nuclear test site, it is unlikely that levels of radiation high enough to be of concern will be encountered. The same is true for naturally occurring radiation. There are only a few natural deposits of radioactive material that are so concentrated that radiation exposure is a problem. There are uranium mines so rich that they cannot be safely operated.
Radiation Absorbed Dose	See RAD.
Radioactive	Having the property of emitting radiation.
Radioisotope	An isotope of an element which undergoes decay of its nucleus, emmitting a particle and/or a photon of energy.
Rare Earth Elements	(Abbreviated: REE) Rare Earth Elements are the Lanthanum series of elements. The IIb Series elements (Scandium and Yttrium) are often considered to be Rare Earth Elements. The Actinide series elements, though chemically related, are usually not considered to be REE's, as only Uranium and Thorium occur in nature to any great extent due to the very short half-lifes of most these elements (see Radian Barite for an exception). Rare Earth Elements IIb Series Scandium Yttrium Yttrium subgroup (Heavy Rare Earth Elements) Lanthanide     Series Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Cerium subgroup (Light Rare Earth Elements) Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Yttrium subgroup (Heavy Rare Earth Elements) Actinide     Series Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium (Chemically related to the Rare Earth Elements) Approximately 5% of the rare earth elements in minerals are replaced by Thorium. This can vary considerably with what rare earth elements are present.
Rational Face(s)	The face presented by a crystalline grain when its growth is bounded, or inhibited, by contact with neighboring crystal growth. The resulting grain, when all crystal faces are inhibited, is referred to as euhedral.
REE	See Rare Earth Elements.
Refining	See smelting.
Refraction	The change in direction of an energy wave (such as light or a seismic wave) as it passes from one medium to another, due to the two media having different velocities of propagation. The energy changes direction toward the higher velocity medium. A gradual change in the velocity of propagation in a medium will cause a gradual bending of the path, toward the zone of higher velocity, of the energy passing through it. The difference in refractive index between air and glass allows a microscope or telescope to magnify an image.
Reniform	Kidney shaped. Similar to botryoidal and colloform.
Resinous	Having the appearance, or luster, of a resin - a solid or semisolid, viscous substance (a mass of semi-melted lumps)
Ropy pahoehoe	Ropy pahoehoe is the most common surface texture of pahoehoe flows. The numerous folds and wrinkles ("ropes") that are characteristic of ropy pahoehoe form when the thin, partially solidified crust of a flow is slowed or halted (for example, if the crust encounters an obstruction or slower-moving crust). Because lava beneath the crust continues to move forward, it tends to drag the crust along. The crust then behaves like an accordion that is squeezed together--the crust is flexible enough to develop wrinkles or a series of small ridges and troughs as it is compressed and driven forward. Image courtesy of the U.S. Geological Survey.
Rosette	A radial cluster of crystals arranged in a circular pattern about a center point, resembling a rose in appearance. The orientation of crystals may be random to each other. And excellent example of rosettes is Kasolite.
S
Safety fuse	A train of mealed black powder, enclosed in a waterproof tube of cotton or jute, which burns at a uniform rate, usually about 1.25 cm per second. Used in mining for initiating a non-electric detonator that in turn fires an explosive charge.
Sand	See clast.
Sandstone	A sedimentary mineral consisting of sand cemented together by deposited silica, calcium carbonate, uraninite or other mineral(s).
Scepter	A crystal form that is characterized by a sudden increase in diameter at its termination, resembling a royal scepter.
Schist	A fine grained metamorphic rock whose layered grains are platy and aligned. It is finer grained than gneiss, which it can be further modified to. It is formed from basalt (igneous rock), shale (sedimentary rock), or slate (metamorphic rock), by high heat and pressure. It is composed mostly of biotite, muscovite (light mica) and quartz, and may contain green chlorite, garnets, staurolite and kyanite.
Sectile	Said of a mineral that can be cut with a knife. An example of such a mineral is Rauvite.
Sedimentary Rock	Rock formed by the deposit of minerals from the action of water. It has several sources: By the mechanical erosion and mixing of the parent rock(s), with the resulting particles moved and deposited when the water is no longer turbulent enough to suspend it. They are then bonded by pressure and/or a bonding material, such as calcium carbonate; By deposition of mineral(s) from a water solution by the chemical reaction of the component anion(s) and cation(s) in the solution to form a less soluble compound. For example, walpurgite; By the oxidation, or reduction, of the anion(s) of a dissolved mineral, making a less soluble mineral that deposits out. For example, wood petrified by uraninite that was reduced by the decaying wood. By efflorescence, the evaporation of the solvent water. For example, threadgoldite. Note: these last three are examples of an authigenic mineral.
Seismic	A term for vibrations within the earth, both natural (i.e.: earthquakes) and artificial (i.e.: mine blasting).
Shaft	A vertical, horizontal or inclined passage providing access from the working surface of underground ore bodies.
Shinarump     Conglomerate	A geologic layer found under the Colorado Plateau, Great Basin province, Paradox basin and San Juan basin. In the Petrified Forest National Park region, it is a 16 meter thick yellow conglomerate, containing petrified wood, above 65 meter thick layer of chocolate sandstone and shale [Moenkopi Formation] and below a layer of variegated gypsiferous clay [Chinle Formation].
Sievert	(symbol: Sv) The Sievert is the S.I. standard unit of measure for the biologically effective radiation dose. It is the quantity of radiation that will deposit 1 joule of energy into 1 kilogram of the target material times the quality factor for that type of radiation. The Sievert is the dose of radiation, in Grays, that was received times the quality factor. To make it conform to the older standards of radiation dose measurements, the centiSievert is usually used, as 1 centiSievert = 1 RAD per hour of radiation flux.
Silica	Silicon dioxide, SiO2, a white or colorless crystalline compound. It occurs abundantly in nature as quartz, sand, flint, agate, and many other minerals. When it occurs as a dust and is inhaled, it can cause the lung disease silicosis.
Silicate	A class of chemical compound, and in particular minerals, that have silicon oxides are their anion The tutorial on Silicates is recommended. There are six subclasses of silicates: Nesosilicates Sorosilicates Inosilicates Cyclosilicates Phyllosilicates Tectosilicates
Silky	A smooth, shiny, luster having a very fine, aligned, texture similar to the luster of silk.
Sink and Float Process	See Dense Media Separation
Smelting	Extracting metal(s) from the concentrated ore by pyrometallurgical (heating) processes. Reducing agents, such as coke, may or may not be used.
Sodic	Containing the element Sodium (Na).
Specific     Gravity	(Symbol: r) • The ratio of the mass of a solid or liquid to the mass of an equal volume of pure water at the temperature of 3.9°C (~39°F). Often expressed as grams per cubic centimeter. • For a gas, the mass of the gas to that of an equal volume of air, or hydrogen, under at a given temperature and pressure.
Sphenoidal	Wedge shaped. A tabular habit having the appearance of a book. A good example of this habit is Metatorbernite.
Spherulite	A habit of occurring in radial, spherically shaped, clusters. A rounded aggregate of acicular crystals radiating from a common center formed from molten material. A rounded cluster of acicular crystals formed in sedimentary rock. A radial cluster, which see. This is taken to be a secondary definition of the term. A good example of this habit is Haiweeite. Compare with botryoid habit.
Squib	A small device used to initiate deflagration in susceptible blasting agents. Small squibs are used in the movie industry to give the illusion of bullet impacts on walls and in dirt.
Stalactite	An icicle-shaped mineral deposit, usually of Calcite or Aragonite, which hangs down from the ceiling of a cave. It is formed from the dripping of mineral-rich water that slowly evaporates and deposits some of its dissolved mineral. It is derived from the Greek word stalaktos, meaning dripping. Compare with stalagmite.
Stalagmite	A mineral deposit usually in the shape of a conical pillar, commonly made of calcite or aragonite. It is built up on the floor of a cave from the dripping of mineral-rich water that slowly evaporates and deposits some of its dissolved mineral. It is derived from the Greek word stalagma, a drop. A pillar of mineral, usually made of calcite or aragonite, that extends from the floor to the roof of a cave. It is usually formed when a stalagmite, described above, and a stalactite grow together to form a single structure. A pillar-shaped mineral deposit, usually made of calcite or aragonite, that grows on the wall of a cavern, and appears to possibly have been free standing. Compare with stalactite.
Stope	A void created by extracting ore in an underground mine.td>
Stoping	The process of extracting ore from an underground mine.
Streak	The mark left on a white (or black) ceramic plate when a mineral is scratched against it. The color of the streak is used in identifying the mineral.
Streak Test	A test used in identifying a mineral using color of the mark, or streak, left on a white (or black) ceramic plate when a mineral is scratched against it.
Striation(s)	Visible, very fine parallel markings, usually on the surface of a mineral, which are long and thin. They are usually differences of color and/or physical ridges that cause reflective bands. They often occur parallel to the main axis of the crystal of the mineral. When they are extremely fine in texture they can give the crystal a silky luster.
Stripping Ratio	The number of units of waste rock or overburden which must be removed to expose one unit of ore in an open pit mine.
Strombolian     Eruption	An explosively violent volcanic eruption, producing much shreadded lava and little or no lava flow. It is named for the type of eruptions characteristic of the volcano on the island of Stromboli, whose main volcano is Serra Vancori, in the Lipari (Aeolic) Islands off northeast Sicily, southern Italy, in the Tyrrhenian Sea.
Sublimate	Changing directly from a solid to a gas, or a gas to a solid, without becoming a liquid. The condensate from such a change is also called a condensate. Water and Sulfur have this property.
Substrate	A thin layer of mineral, often of calcium carbonate, CaCO3, underlying a mineral deposit, and separating it from the host rock. This is usually seen when the mineral deposit is incompatible for some reason with the host rock. Uranium minerals that contain highly reactive radicals, usually halides and hydroxide, are seen to form on a calcium carbonate substrate. An example of a substrate providing a compatible deposit location can be seen with Weeksite.
Sunburst	A cluster of crystals radiating in a circular pattern from a center point. The crystals are oriented side by side to each other. It is often found when a mineral having an acicular crystal form whose habit is to form radial clusters grows with a crack of the host rock. And excellent example of sunburst clusters is Haynesite.
Supergene	Referring to a mineral deposit, or enrichment, by descending solutions. Also refers to those solutions.
Supergene Enrichment	Enrichment of a near surface mineral deposit by oxidation of sulfide ore, causing acidic solution that dissolves the metallic content of the ore. As the solution penetrates deeper into the ground, the dissolved mineral(s) are precipitated out, causing a layer of enrichment below the upper levels of the oxidation zone.
Sv	See Sievert.
Syenite	An igneous rock, composed primarily of alkali feldspars (usually orthoclase, microcline or perthite) and a small amount of plagioclase, together with one or more mafic minerals, particularly hornblende. It has no, or extremely little, quartz. From the Latin word for stone, Syenites, for stone of Syene, an ancient city in southern (upper Nile, now known as Aswan) Egypt.
T
Tabular	Tending to split into thin flat pieces, usually coarser than Micaceous. A good example of this habit is Metatorbernite.
Tailings	The fine grained remnant of ore that has had the economically extractable valuable material removed from it by the concentration process.
Termination	The end of a crystal that is much longer than it it is wide or thick. For example, the terminations of these Kasolite crystals are transparent, while their bodies are translucent.
Theory of Hot Radicals	This is a theory of occurence of Uranyl minerals that if they contain highly reactive anions, having a valence of -1 (i.e.: halides and hydroxide), in their make-up they will form preferentially on either Calcite or Aragonite, and rarely lime, all being forms of Calcium Carbonate (CaCO3). A Uranyl mineral that contains one or more oxygen rich anions, such as arsenate, phosphate, silicate or sulfate, can occur on or in silica or a silicate host rock. However, if in addition to these anions it also contains one or more highly reactive -1 valence anions, the mineral will avoid forming on, or in, a silicate host rock, and have a formation preference for a Calcium Carbonate (Calcite, or Aragonite) substrate instead. This theory is postulated from observations by Paul M. Schumacher.
Thorium	Element 90 One naturally occurring radioactive isotope: Th-232 (~100%): t½ (a): 1.41 × 1010 years t½ (SF): >1021 years Th-234 (~0% - Uranium-238 decay daughter): t½ (b): 24.10 days Uses: power generation fission nuclear weapons (converted to U-233) gas lantern mantles ceramics interesting minerals
Tonne	Metric ton, 1,000 kilograms. This is approximately 2.2 English tons.
Transparent	Having the property of transmitting light so that images can be seen through the mineral as if there were no intervening mineral, except possibly with the color biased to that of the transparent mineral. See diaphaneity.
Translucent	Having the property of transmitting light, but causing sufficient diffusion of the light to prevent perception of distinct images. See diaphaneity.
Triboelectric	The property of certain crystals of generating an electric charge when in contact with another material. See piezoelectric for comparison.
Twin	Two intergrown crystals that share a common internal or external axis or plane. An example of this is Thorianite.
Type Locale	The source location of the mineral specimen(s) first used to determine and describe a mineral's physical, optical and chemical properties.
U
Ultrabasic	A term used to describe igneous rock that is enriched in magnesium and iron, and contains very little silica. Often termed ultramafic, a mnemonic for its magnesium and iron (ferrum) content.
Ultramafic	See ultrabasic.
Ultraviolet Light	Electromagnetic radiation that is not readily visible having the wavelength of from 4 nanometers (on the border of the x-ray region) to 400 nanometers (just beyond the violet in the visible spectrum). There are four bands of ultraviolet light: Long Wavelength (UV-A) - 315 to 400 nm - this is the band of ultraviolet light closest to that of visible light (400 to 700 nm). It is the easiest to produce, and most often used in mineralogy for stimulating fluorescence. Medium Wavelength (UV-B)- 280 to 315 nm - intermediate between the UV-A and UV-C bands, it is seldom used in mineralogy. Short Wavelength (UV-C) - 100 to 280 nm - being more energetic, more minerals fluoresce under this ultraviolet light. Those that fluoresce will often do so more strongly under UV-C. Vacuum Ultraviolet Light - 4 to 100 nm - just below soft x-rays, and incapable of propagating any distance through air. Thus its being termed vacuum ultraviolet light.
Unit Cell	Measured in Ångströms, the unit cell is the smallest divisible unit of a mineral that still possesses the atomic symmetry and physical properties of the mineral. It is a group of atoms, ranging from four to as many as 1000, that have a certain geometric structure relative to one another. The atoms are arranged in a "box" as a single entity, having parallel sides, called the unit cell. The unit cell is repeated, by simple geometric translation, to form a crystal, with each cell in the crystal identical to every other. The atoms may be located at the corners, on the edges, on the faces, or wholly enclosed within the cell. This is the "ordered internal arrangement" of a crystal. The atoms may be at the corners, on the edges, on the faces, or wholly enclosed in the unit cell, and each cell in the crystal is identical to all other unit cells in structure and alignment. This is what is meant by an "ordered internal arrangement" in the definition of a mineral, and is why crystals have their shapes, cleavages, and regular properties. The dimensions of the unit cell give its volume and are calculated as follows: Crystal System Unit Cell Volume Isometric V = a·3 Tetragonal V = a·2·c Hexagonal V = a·2·c sin(60°) Trigonal V = a·2·c sin(60°) Orthorhombic V = a·b·c Monoclinic V = a·b·c sin(beta) Triclinic V = a·b·c · [1- cos(2·a) - cos(2·b) - cos(2·g)] + 2[cos(a) cos(b) cos(g)]1/2 Where a, b, and c are the unit cell axes dimensions and a, b, and g are the inclination angles of the axes in the unit cell, relative to each other. Den(Calc) = (Mw · Z) / (V · Na) grams/cubic centimeter Where:         V       = Cell Volume (in cubic Angstroms)         Z       = Atoms per Cell         Mw   = Molecular Weight (grams/mole)         Na     = Avogadro's constant (0.60225 · 1024)
United States Geological Survey	The U.S. Geological Survey is an agency of the U.S. Government that studies the geology and natural resources, of the United States. It often best known for gathering topographical information that is publicly available as maps (this function is separate from the Dept. of Defense's Mapping Agency).
Uranium	Element 92 Two naturally occurring radioactive isotopes of consequence: U-235 (0.7%): t½ (a): 7.1 × 108 years t½ (SF): 1.9 × 1017 years U-238 (99.3%): t½ (a): 4.51 × 109 years t½ (SF): 1.0 × 1016 years Uses: power generation fission nuclear weapons coloring (yellow) for glass and ceramics interesting minerals
Uranyl	(UO2+2) A cation of hexavalent uranium with two oxygen atoms, having a valence of +2. All but five (quadravalent uranium: Brannerite, Coffinite, Uraninite, Uranmicrolite and Uranpyrochlore) of the recognized uranium minerals are of the uranyl form of uranium.
U.S.G.S.	See United States Geological Survey.
V
Valence	The number of electrons that an atom will lose, add, or share when it reacts with other atoms. Also see anion and cation.
Vein	• A regularly shaped and lengthy occurrence of an ore - a lode • A layer of mineral that is relatively thin in relation to its width and breadth, and may sometimes be at some angle to the layers of host rock • An example of a vein can be seen with this image of a vein of Zippeite in a vein of Uraninite.
Vitreous	A mineral appearance that resembles the appearance of glass (glassy) - appearing to have been melted and resolidified into a glass-like state. A good example of this habit is Samarskite-(Y).
Volcanic	Of, resembling, or caused by a volcano or volcanoes; Produced by or discharged from a volcano; Characterized by the presence of volcanoes; Powerfully explosive.
Volcano	An opening in the earth's crust through which molten lava, ash, and gases are ejected.
Vug	A small cavity in a rock or vein, often with a mineral lining of different composition from that of the surrounding rock. An image of several opened vugs containing Cuprosklodowskite, Metatyuyamunite, Metatorbernite, and one with possible Saléeite. Compare with miarolitic.
W
Weather	verb The slow disintegration of a mineral due to the effects of its exposure to the atmosphere (oxygen and water) and weather (sun, rain, heat, freezing, etc.).
Weathering	The process of chemical and mechanical disintegration of rock and minerals by exposure to the atmosphere, sun, rain, heat, cold, oxidation and reaction with other environmental agents.
Wheal	A small, isolated hill.
White Light	Visible light that has all of the visible spectrum present, so it appears white
Working Stope	An underground working area used for extracting ore in an underground mine.
X
X-ray	Non-nuclear radiation generated by extremely high (solar surface like) temperatures or the bombardment of heavy metals, such as tungsten, by kilovolt electrons in X-ray machines. X-rays have the wavelength between 10-11 to 10-08 meters (0.1 to 100 Å), placing them between ultraviolet light and g-rays. X-rays are used in medical diagnostics and to measure the Separation of atoms and crystalline planes within crystals.
Y
Z