Derriksite

Derriksite is a very rare uranium mineral with the chemical formula Cu₄(UO₂)(SeO₃)₂(OH)₆•H₂O. It is a secondary mineral that contains copper, uranium and the rarer selenium. It is a bright green to duller bottle green colour. Its crystal habit is acicular, it is most likely to be found along with the uranyl selenium mineral demesmaekerite, but derriksite is much rarer than demesmaekerite. It is named after Jean Marie Francois Joseph Derriks (1912–1992), geologist and administrator of the Union Minière du Haut Katanga (UMHK). It has a Mohs hardness of about 2.[1]

Derriksite
Crystals of copper-uranium-selenite derriksite (bottle green) on a bed of malachite, the matrix is selenium-rich digenite
General
Category	Oxide minerals
Formula (repeating unit)	Cu4(UO2)(SeO3)2(OH)6•H2O
Strunz classification	4.JG.30
Crystal system	Orthorhombic
Crystal class	Pyramidal (mm2) H-M symbol: (mm2)
Space group	Pn21m
Identification
Colour	Bottle green, green
Cleavage	{???} perfect, {010} good
Diaphaneity	Translucent
Specific gravity	4.72
Other characteristics	Radioactive