What is "perhamite"

n. (context mineralogy English) A hexagonal-dihexagonal dipyramidal mineral containing aluminum, calcium, hydrogen, oxygen, phosphorus, and silicon.

Perhamite is a phosphate mineral with the formula Ca Al(SiO)( P O)(OH)·16.5( HO). It occurs in rare isolated masses in amblygonite-rich pegmatite deposits throughout the world. It was discovered in platy sheed form of 1mm hexagonal crystals. It was first described in 1977 by P.J. Dunn and D.E. Appleman from pegmatite collected from Bell Pit, Newry, Maine. Other specimens have been found in Kapunda, South Australia, in Silver Coin mine near Humboldt County, Nevada and various locations throughout Europe.