Oppenheimerite

Oppenheimerite is a very rare uranium mineral with the formula Na₂(UO₂)(SO₄)₂•3H₂O.^[2][3] Chemically related minerals include fermiite, natrozippeite, plášilite, belakovskiite and meisserite.^{[4][5][6][7][8]} Most of these uranyl sulfate minerals were originally found in the Blue Lizard mine, San Juan County, Utah, US.^[9] The mineral is named after American Theoretical physicist J. Robert Oppenheimer.^[3]

Oppenheimerite
General
Category	Sulfate mineral
Formula	Na2(UO2)(SO4)2•3H2O
IMA symbol	Ohm[1]
Crystal system	Triclinic
Crystal class	Pinacoidal (1) (same H-M symbol)
Space group	P1
Unit cell	a = 7.96, b = 8.20, c = 9.81 [Å]; α = 65.97° β = 70.28°, γ = 91.46° (approximated), Z = 2
Identification
Color	Pale greenish-yellow
Crystal habit	prismatic
Cleavage	{110}, {011} and {101}, good
Fracture	Irregular
Mohs scale hardness	2.5
Luster	Vitreous
Streak	White
Diaphaneity	Transparent
Density	3.36 (calculated) (approximated)
Optical properties	Biaxal (+)
Refractive index	nα=1.54, nβ=1.63, nγ=1.59 (approximated)
Pleochroism	Very pale greenish-yellow (X), pale greenish-yellow (Y), greenish-yellow (Z)
2V angle	72o (measured)
Ultraviolet fluorescence	Greenish-white
Other characteristics	Radioactive
References	[2][3]

Association and origin

Oppenheimerite is associated with other sulfate minerals: fermiite, bluelizardite, wetherillite, blödite, chalcanthite, epsomite, gypsum, hexahydrite, kröhnkite, manganoblödite, sideronatrite, and tamarugite.^[2]

Crystal structure

The crystal structure of oppenheimerite is of a new type. It contains chains of the (UO₂)(SO₄)₂(H₂O) composition, connected with two types of sodium polyhedra.^[2]