Mineral Information and Data:

Carnotite  
K2(UO2)2(VO4)2 • 3H2O [CNMNC approved formula]

Named for Marie-Adolphe Carnot (1839-1920), French mining engineer and chemist.

IMA status : Valid species (Pre-IMA 1899) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
40.02a.28.01  
  (40) Hydrated Phosphates
  (40.02a) where A++ (B++)2 (XO4) · x(H2O), containing (UO2)++
  (40.02a.28)
  
Nickel-Strunz
(10th edition) :
04.HB.05
  (04) Oxides and Hydroxides
  (04.H) V[5+,6+] Vanadates
  (04.HB) Uranyl Sorovanadates
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 10.47 Ǻ, b = 8.41 Ǻ, c = 6.59 Ǻ, β = 103.8°
Crystal Habit: Crystals microscopic, rhombic or diamond-shaped outline; disseminated, coatings, powdery, masses crusts
  
Color: Bright yellow to golden yellow, greenish yellow
Diaphaneity: Translucent
Luster: Dull, earthy; silky when crystalline
Hardness (Mohs): 2
Measured Density: 4.70 g/cm3
Cleavage: 1; {001} perfect, micaceous
Tenacity: Micaceous
Streak: Strontian-yellow
  
Geologic Setting: An important ore mineral of uranium, typically in paleochannels in sandstone
Colorado Plateau-type U–V deposits, found near fossil carbonaceous matter, and in calcretes and near playas; an alteration product of uraninite, montroseite, or davidite.
Mineral Association: Tyuyamunite, metatyuyamunite, volborthite, tangeite, metatorbernite, rossite, hewettite, other U–V oxides, gypsum, barite
Ore deposits: A chief primary ore mineral of uranium.
  
Other Properties: Radioactive.
Comments: Water content is partly zeolitic and varies with humidity at ambient temperatures. Readily soluble in acids.

 

Carnotite
Origin: Firefly-Pigmay mine, La Sal district, San Juan Co., Utah, U.S.A.
Sample size: 8 x 6 x 2 cm, crystals about 0.5 mm
Photo: Tom Loomis

 

Carnotite
(zoom-in of above)

 

Carnotite
Yellow earthy crust on dark, black davidite matrix
Origin: Olary, South Australia, Australia
Sample size: 4.5 x 4 x 2 cm
Photo: Tom Loomis

 

Carnotite
(zoom-in of above)

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