Formula: Cu₂Mg₂(PO₄)₂(OH)₂ · 5H₂O

Species:

Colour: Bluish green to deep blue, turquoise-blue

Hardness: 2½

Specific Gravity: 2.73

Crystal System: Monoclinic

Name: Named for William H. Nisson (1912–1965), amateur mineralogist, mineral collector and dealer, of Petaluma, California, USA, who first noted the mineral.

Type Locality: Llanada Copper Mine, Panoche, San Benito Co., California – USA