Ternary (M22M3) composition diagram showing the location of empirical compositions for paulkerrite group members. Blue crosses correspond to Mg dominant at the M1 site, whereas red crosses have Mn dominant at M1. — Photo: Ian E. Grey, Stephanie Boer, Colin M. MacRae, Nicholas C. Wilson, William G. Mumme, and Ferdinando Bosi · CC BY 4.0
Paulkerrite
Paulkerrite is an IMA-recognized mineral species in the phosphate class, with the chemical formula KMg₂TiFe³⁺₂(PO₄)₄(OH)₃·15H₂O.
It crystallizes in the orthorhombic crystal system (space group Pbca).
Key properties: Mohs hardness 3; specific gravity 2.36; White streak; Vitreous luster; optically biaxial.
IMA symbol Pke, IMA status: approved, named in 1983.
An alteration product of triplite in complex zoned granite pegmatites.
It is found associated with Triplite, bermanite, phosphosiderite, leucophosphite, strengite, switzerite (7U7 Ranch, Arizona, USA).
The mineral was named to honor Dr. Paul Francis Kerr (1897–1981), Professor of Mineralogy, Columbia University, New York City, New York, USA.