Sengierite

Sengierite is a rare oxide and hydroxide mineral, chemically a copper and uranyl vanadate, belonging to the carnotite group. Its chemical formula is Cu₂(OH)₂[UO₂|VO₄]₂·6H₂O.^[2][3]

Sengierite
General
Category	Oxide and Hydroxide
Formula	Cu2(OH)2[UO2|VO4]2·6H2O
IMA symbol	Sgi[1]
Crystal system	Monoclinic
Space group	Monoclinic 2/m
Identification
Color	Olive-green, yellowish green
Crystal habit	Flattened thin plates, coatings
Cleavage	Perfect on {001}
Tenacity	Brittle
Mohs scale hardness	2.5
Luster	Adamantine, vitreous
Streak	Light green
Diaphaneity	Transparent
Specific gravity	4.05
Density	4.05 g/cm3 (measured) 4.1 g/cm3 (calculated)
Refractive index	nα = 1.760 – 1.770 nβ = 1.920 – 1.940 nγ = 1.940 – 1.970
Pleochroism	X: Bluish green, Y: Olive-green, Z: Yellowish green to colorless
2V angle	Measured: 37° to 39°, Calculated: 36°
Other characteristics	Radioactive

Sengierite was first discovered at the Luiswishi Mine about 20 kilometres (12 mi) north of Lubumbashi in Katanga Province in the Democratic Republic of the Congo and was first described in 1949 by Johannes F. Vaes and Paul F. Kerr, the mineral was named after Edgar Sengier (1879–1963), a former director of the Union Minière du Haut Katanga.^[4]