IMA Code	Definitions
A	Accepted - usually followed by year and sequence number
G	Accepted - grandfathered
GP	Accepted - grandfathered, provisional

Most minerals containing over 5% of Uranium and/or Thorium rapidly, in geologic terms, become metamict. This results in the mineral's crystal structure becoming essentially glass-like at the atomic level. For this reason, the cleavage of these minerals may be unknown, as naturally occurring 'crystals' may no longer be truely crystaline.

Minerals that show a crystal form, but have no cleavage, and whose fracture is either conchoidal or brittle, should be suspect of being metamict.

The cause for uranium and thorium minerals going metamict is not the g-ray radiation, but 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 relieced within the mineral. This causes a masive local disruption of the crystal structure, that over time, 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.

• the magnitude of its uranium and thorium content
• its age

Pure uranium and thorium have long half-lives, and therefore, when pure, have a low specific radioactivity. As they age, more of their daughter elements become present, increasing the specimen's specific radioactivity. As the daughter elements approach their homeostasic ratio with the their parent, their populations will decrease with the decreasing population of their parent. If the uranium and thorium daughters were absent when the mineral was deposited, and not removed or deposited from elsewhere since, this can give an estimate of the specimen's age.

The homeostasic ratio, where the population of the daughter element follows in ratio the population of its parent radioactive element, can only be approached, and never reached, much as a wall can only be approached, and never reached, if one approaches it by continually halfing the distance. However, after about 10 half-lifes of the shorter lived daughter, the difference between the actual and homeostasic ratios will be less than 0.1%.

All gamma-radiation levels given for specimens were made using a Digilert-50 geiger-meuller counter, using GeigerGraph software and an adapter cable to allow computer monitoring and averaging. The specimen is oriented to give the highest reading. The reading is the average of 30 minutes at a distance of 2.5 centimeters (approximately 1 inch) from the surface of the specimen to the side of the geiger counter containing the geiger tube.

When taking the gamma radiation level of a specimen, it is important that the conditions be the same for when the background count and measurement are taken. This is especially true for specimens that are small or have very little radioactive material. In my personnal experience, placing my body between the geiger counter and my collection or not (sitting back or leaning forward in my chair), results in a change in background count (30 minute average) from 18 cpm down to 29 cpm.

A military surplus AN/PDR-27R or old Civil Defense CDV-700 geiger-meuler counter will give much higher count readings, as they use a larger geiger-meuller tube which presents a larger target to gamma-rays. These are not used as their readings are in RAD's, they do not give counts per minute, and they require nearly constant calibration. They are usually supplied many decades out of date.

Mineral data entered with the notation "(x Specimens Examined)" are from the examination of personnally owned specimens when no information is available elsewhere. The 'x' is the number of different specimens checked. This information may not be completely reliable due to the characteristics of that checked specimen possibly not being representitive of that mineral.

The ultraviolet light fluorescence results of personnally examined specimens were at room temperature with no prior heating. Heating, particularly if done to red heat by a blow-pipe, can improve, or bring about, fluorescence (Sterling Gleason; Ultraviolet Guide To Minerals; van Nostrand Co., Inc.; 1960).