Uranophane

Uranophane (Ca(UO₂)₂(SiO₃OH)₂·5H₂O), also known as uranotile, is a rare calcium uranium silicate hydrate mineral that forms from the oxidation of other uranium-bearing minerals. It has a yellow color and is radioactive.

Uranophane
General
Category	Uranyl neso- and polysilicates
Formula	Ca(UO2)2[HSiO4]2·5H2O
IMA symbol	Urp-α[1]
Strunz classification	9.AK.15
Crystal system	Monoclinic
Crystal class	Sphenoidal (2) (same H-M symbol)
Space group	P21
Unit cell	a = 15.85 Å, b = 6.98 Å c = 6.64 Å; β = 97.45°; Z = 2
Identification
Formula mass	586.36 g/mol
Color	Light yellow, lemon-yellow, honey-yellow, straw-yellow, green-yellow
Crystal habit	Crystals occur as stellate needle aggregates; as fibrous crusts, and massive
Cleavage	{100} Perfect
Fracture	Uneven
Tenacity	Brittle
Mohs scale hardness	2.5
Luster	Vitreous to pearly; waxy or dull when massive
Streak	Yellowish white
Diaphaneity	Translucent to subtranslucent
Specific gravity	3.81–3.90
Optical properties	Biaxial (−)
Refractive index	nα = 1.643 nβ = 1.666 nγ = 1.669
Birefringence	δ = 0.026
Pleochroism	Weak; X = colorless; Y = pale canary-yellow; Z = canary-yellow
2V angle	32° to 45°, measured
Ultraviolet fluorescence	Weak yellow-green under both short and long UV
Other characteristics	Radioactive
References	[2][3][4]

Alice Mary Weeks, and Mary E. Thompson of the United States Geological Survey, identified uranophane in 1953.^[5]

Classic samples have been produced at Madawaska Mine near Bancroft, Ontario.^[6]

Cuprosklodowskite (green) altering to Uranophane (yellow needles). Musonoi Mine, Kolwezi, Katanga, Democratic Republic of Congo