Dark green platy crystals of the extremely rare Ca-Ni phosphate mineral cassidyite from the TL for otwayite in Otway (Otway Nickel Deposit, Nullagine, East Pilbara Shire, Western Australia, Australia). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Cassidyite
Cassidyite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Ca₂Ni(PO₄)₂·2H₂O.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Fairfieldite structural group.
Key properties: optically biaxial.
IMA symbol Cdy, IMA status: approved, named in 1966.
An alteration product of a highly weathered iron-nickel meteorite, produced through alteration of schreibersite.
It is found associated with Reevesite, goethite, nickelian maghemite, jarosite, nickel-rich serpentine, apatite, lipscombite.
In honor of Dr. William A. Cassidy, who mapped the Wolf Creek, Australia, crater in 1953.