Mineral Information and Data:

Autunite  
Ca(UO2)2(PO4)2 • 10-12H2O [CNMNC approved formula]

Named after the locality; Autun, Saone-et-Loire, France.

IMA status : Valid species (Pre-IMA 1852) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
40.02a.01.01  
  (40) Hydrated Phosphates
  (40.02a) where A++ (B++)2 (XO4) · x(H2O), containing (UO2)++
  (40.02a.01) Autunite Group
  
Nickel-Strunz
(10th edition) :
08.EB.05
  (08) Phosphates, Arsenates, Vanadates
  (08.E) Uranyl Phosphates and Arsenates
  (08.EB) UO2:RO4 = 1:1
  
Crystal system: Tetragonal System
Point group (H-M): 4/mmm (or 4/m 2/m 2/m) — ditetragonal-dipyramidal
Unit cell: a = 6.989 Å, c = 20.63 Å
Crystal Habit: Crystals thin to thick tabular with rectangular or octahedral shape; fan-like groups, crusts, foliate
Twinning: On {110}
  
Color: Sulfur-yellow, lemon-yellow, green-yellow to pale green, may be dark green to greenish black
Diaphaneity: Transparent to translucent
Luster: Vitreous, pearly on {001}, masses dull
Hardness (Mohs): 2 to 2.5
Measured Density: 3.05 to 3.20 (varies with hydration) g/cm3
Cleavage: 2; {001} perfect, {100} indistinct
Streak: Pale yellow
  
Geologic Setting: A secondary mineral derived from primary uranium-bearing minerals under
oxidizing conditions, in hydrothermal veins, granite pegmatites, etc.
Mineral Association: Meta-autunite, torbernite, phosphuranylite, saléeite, uranophane, uranophane-beta, sabugalite
Ore deposits: A chief primary ore mineral of uranium.
  
Synonyms/varieties: Lime uranite
Luminescent Properties: Fluoresces strong yellow-green in UV light.
Other Properties: Radioactive.
Comments: Dehydrates in air to meta-autunite;

 

Autunite
Small crystals of autinite with pinkish feldspar and black schorl, left photo green fluorescence of autunite
Origin: Ferguson mine, Pennington Co., South Dakota, USA
Sample size: about 2 cm
Photo: Tom Loomis

 

Autunite
(zoom-in of above)

 

Autunite
Origin: Dahl mine, Mt. Spokane, Washington, U.S.A.
Sample size: 1.6 x 1.5 cm x 4 mm
Photo: Tom Loomis

 

Autunite
Origin: Daybreak mine, Spokane, Washington, United States
Sample size: 7 x 5 x 2.5 cm
Photo: Tom Loomis

 

Autunite
(zoom-in of above)

 

Autunite
Origin: Daybreak Mine, Spokane Co., Washington, U.S.A.
Ex. Gary Hansen, Harvard University collections
Sample size: 6.7 x 5.7 x 3.8 cm
Photo: Rob Lavinsky

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