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Liebigite crystals from the Ralston Buttes District, Jefferson County, Colorado
Category Carbonate mineral
(repeating unit)
Strunz classification 5.ED.20
Crystal system Orthorhombic
Crystal class Pyramidal (mm2)
(same H-M symbol)
Space group Bba2
Unit cell a = 16.699, b = 17.557
c = 13.697 [Å]; Z = 8
Colour Green to yellowish-green
Crystal habit Rare as short prismatic crystals; scaly or granular, in aggregates, crusts, and films
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 [1][2][3]

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.[1][2][3]

It was first described in 1848 for an occurrence in Adrianople, Edirne Province, Marmara Region, Turkey.[1] It was named for German chemist Justus von Liebig (1803–1873).[3]