Nissonite

Nissonite is a very rare copper phosphate mineral with formula: Cu2Mg2(PO4)2(OH)2·2H2O. It crystallizes in the monoclinic crystal system typically as crusts, tabular crystals, and diamond-shaped crystals. The color is blue-green. It has a light green streak, a Mohs hardness of 2.5 and a specific gravity of 2.73. Cleavage is [100] distinct.

Nissonite was discovered in 1966 and was named after W. H. Nisson. It is from Llanada copper mine, near Llanada, San Benito Co., California.