Liebigite

Liebigite
240px Liebigite crystals from the Ralston Buttes District, Jefferson County, Colorado
General
Category	Carbonate mineral
Formula (repeating unit)	Ca2(UO2)(CO3)3·11H2O
Strunz classification	05.ED.20
Crystal symmetry	Orthorhombic pyramidal H-M symbol: (mm2) Space group: Bba2
Unit cell	a = 16.699 Å, b = 17.557 Å, c = 13.697 Å; Z=8
Identification
Colour	Green to yellowish-green
Crystal habit	Rare as short prismatic crystals; scaly or granular, in aggregates, crusts, and films
Crystal system	Orthorhombic
Cleavage	Distinct on {100}
Tenacity	Brittle
Mohs scale hardness	2½ - 3
Lustre	Vitreous, pearly
Diaphaneity	Transparent, translucent
Specific gravity	2.41
Optical properties	Biaxial (+)
Refractive index	nα = 1.497 nβ = 1.502 nγ = 1.539
Birefringence	δ = 0.042
Pleochroism	Visible: X = nearly colourless Y = Z = light yellowish green
2V angle	37° to 42°
Ultraviolet fluorescence	Strong green to blue-green under short and long wave UV
References

Liebigite is a uranium carbonate mineral with the chemical formula: Ca₂(UO₂)(CO₃)₃·11H₂O. It is a secondary mineral occurring in the oxidizing zone of uranium-bearing ores. It is green to yellow green in colour. It has a Mohs hardness of about 3. Liebigite, like some other uranium minerals, is fluorescent under UV light and is also translucent. It crystallizes in the orthorhombic system, but only rarely forms distinct crystals. It typically forms encrustations or granular aggregates.

It was first described in 1848 for an occurrence in Adrianople, Edirne Province, Marmara Region, Turkey. It was named for German chemist Justus von Liebig (1803–1873).