Outstanding perfect single crystal of the rare carbonate mineral pirssonite from the type locality: Searles Lake, San Bernardino County, California, United States of America. — Photo: David Hospital · CC BY-SA 4.0
Pirssonite
Pirssonite is an IMA-recognized mineral species in the carbonate class, with the chemical formula Na₂Ca(CO₃)₂·2H₂O.
It crystallizes in the orthorhombic crystal system (space group Fdd2).
Key properties: Mohs hardness 3–3.5; specific gravity 2.35–2.38; Vitreous luster; optically biaxial.
IMA symbol Pss, IMA status: approved, named in 1896.
A rare component of saline lake-bed sediments; in a differentiated alkalic massif.
It is found associated with Northupite, trona, gaylussite (Borax Lake, California, USA); shortite, bradleyite, northupite, gaylussite, trona (John Hay, Jr. Well No. 1, Wyoming, USA).
The mineral was named to honor Professor Louis Valentine Pirsson (1860–1919), American petrographer and mineralogist, Yale University, New Haven, Connecticut, USA.