Meisserite

Meisserite is a very rare uranium mineral with the formula Na₅(UO₂)(SO₄)₃(SO₃OH)(H₂O).^[2][3] It is interesting in being a natural uranyl salt with hydrosulfate (hydroxysulfate) anion, a feature shared with belakovskiite.^[3] Other chemically related minerals include fermiite, oppenheimerite, natrozippeite and plášilite.^[5][6][7][8] Most of these uranyl sulfate minerals was originally found in the Blue Lizard mine, San Juan County, Utah, USA.^[9] The mineral is named after Swiss mineralogist Nicolas Meisser.^[4]

Meisserite
General
Category	Sulfate mineral
Formula	Na5(UO2)(SO4)3(SO3OH)(H2O)
IMA symbol	Mss[1]
Crystal system	Triclinic
Crystal class	Pinacoidal (1) (same H-M symbol)
Space group	P1
Unit cell	a = 5.32, b = 11.51, c = 13.56 [Å], α = 102.96°, β = 97.41°, γ = 91.46° (approximated); Z = 2
Identification
Color	Pale green to yellowish-green
Crystal habit	prismatic
Cleavage	{100} and {001}, fair
Tenacity	Very brittle
Mohs scale hardness	2
Luster	Vitreous
Streak	Very pale yellow
Diaphaneity	Translucent to transparent
Density	3.21 (calculated) (approximated)
Optical properties	Biaxal (-)
Refractive index	nα=1.51, nβ=1.55, nγ=1.56 (approximated)
Pleochroism	Colorless (X), pale yellow (Y), pale greenish-yellow (Z)
2V angle	60o
Dispersion	Weak
Other characteristics	Radioactive
References	[2][3][4]

Association and origin

Meisserite is associated with other sulfate minerals: belakovskiite, johannite, chalcanthite, copiapite, ferrinatrite, and gypsum.^[2] It is resulting from post-mining oxidation of the primary uranium mineral - uraninite.^[4]

Crystal structure

The crystal structure of meisserite is unique. The building elements include:^[2]

• pentagonal bipyramids of uranyl groups
• SO₄ groups

These elements link to form chains. Sodium cations are bonded to oxygen atoms in chains, to hydrosulfate groups and water.