Autunite	IMA-GP
Uranium	40.2a.1.1 (Dana Classification Number)
(No Images)	7/E.01-90 (Strunz ID)

Unless sealed in glass, all specimens should be considered to have become Meta-Autunite within a few months of being exposed to ambient air. (See Notes for more information).

Property	Data	Remarks
Named for:	Autun, France, its type locality
Alternate     Name(s):	Lime Uranite Calcium Autunite
Mineral Class:	Phosphates, Arsenates and Vanadates   Uranylphosphates and uranylvanadates with [UO2]2+ - [PO4 | AsO4]3- and [UO2]2+ - [V2O8]6-     Autunite group
Chemical     Formula:	Ca(UO2)2(PO4)2 . 10-12H2O
Chemical     Composition:	Calcium: (Ca) 4.06% Hydrogen: (H) 2.45% Oxygen: (O) 38.93% Phosphorus: (P) 6.28% Uranium: (U) 48.27%	by weight
Molecular     Weight:	986.26	daltons (amu)
Specific     Radioactivity:	(All radiation is for a 1 gram, fully aged specimen) Specific Activity Dose Rate Becquerels Curies  milliRems  hour  microSieverts  hour 8.6402 × 1004 2.34 × 10-06 1.23 123.44 Estimated Average Annual Exposure: 360 mRem (3.6 milliSieverts)
Crystalography:	System: Tetragonal - Ditetragonal Dipyramidal Axial Ratios: a: 1 c: 2.95848 Cell Dimensions: a: 7.009 Å c: 20.736 Å Z: 2 V: 1,018.68 Å3 DenCalc: 3.22 H-M Symbol: 4/m 2/m 2/m Space Group: I4/mmm X-Ray Diffraction:   By Intensity ( I/Io ) (1): 10.3 Å (0.8): 4.96 Å (0.7): 3.59 Å	Autunite Crystal
Habit:	Tabular square crystals dominated by two pinacoid faces. Crystals are often in parallel growths that can have a "fanned-out" look or in rosetta clusters Micaceous Foliated Crusts and earthy masses
Cleavage:	[001] Perfect [010] Poor [001] Poor
Fracture:	Uneven
Moh's     Hardness:	2 - 2.5
Density:	3.1 - 3.2	grams/cm3
Color:	Pale yellow to Yellow to Bright "lemon" yellow to Greenish yellow to Pale green to Green. Often showing a mixture of yellow and green shades in one specimen.
Streak:	Pale yellow to Yellow
Luster:	Vitreous to Pearly, on the main pinacoid. Subadamantine elsewhere.
Diaphaniety:	Transparent to Translucent
Pleochroism:	(x):   (y:)   (z:)
Ultra Violet     Fluorescence:	Long Wave: Yellow to Yellow-green Short Wave: Yellow to Yellow-green
Magnetism:	Non-magnetic
Occurance:
Associated     Minerals:	Secondary mineral to Uraninite. Also Torbernite, Metatorbernite, Uranocircite, Uranophane and other uranium minerals. Minerals   -   Uranium & Thorium mineral links	These are minerals known to be found with Autunite
Localities:	Relatively common Uranium mineral Autunite Localities
Notes:	Strongly radioactive a- and b-particles, g-rays. Crystals are probably metamic. Thin crystals or cleavage sheets are bendable. Autunite can lose water and convert to a different mineral called Meta-Autunite-I of the Meta-Autunite/Metatorbernite group of minerals. With heating, it can produce a Meta-Autunite-II mineral. Neither mineral is found in nature in any appreciable abundance. The conversion is irreversible (see below) and ongoing, and all specimens exposed to ambient air for several months are at least partially converted. Eventually, after many years, the Meta-Autunite will turn to powder. When Autunite dehydrates, the crystals fracture into extremely fine fragments of the mineral Meta-Autunite. These fragments retain the general form of Autunite, and are therefore a pseudomorph of Autunite. While the dehydration can can be reversed, rehydrating back to Autunite, the fragments do not fuse back into a single crystal. When rehydrated, the Autunite becomes, in effect, a pseudomorph of itself. The x-ray diffraction pattern of the rehydrated Autunite will be that of Autunite, but will be somewhat blurred due to slight misalignment of the crystal fragments. Unless done very slowly and carefully, rehydration of Meta-Autunite will cause the re-expanding crystals to push apart, and the pseudomorph crystal to break up. It is believed that over years of dehydration/rehydration cycling is the cause of specimens turning to powder.