|Transparency||Transparent to translucent|
|Hardness||3 to 4|
|Optical Character||Biaxial - ; Double Refractive|
|Fluorescence||Violet under s w ultraviolet|
|Comments||Attacked by and soluble in acids|
Phosphophyllite (fos-FOFF-uh-lite) is a zinc phosphate hydrate with the formula Zn2(Fe,Mn)(PO4)2.4H2O. Its name is derived from the Greek phyllon ("leaf") and lite ("mineral") in allusion to the common crystal color.
Phosphophyllite ranges in color from colorless to green to blue, and it rarely occurs in faceting quality. It produces a beautiful gem, but the low hardness of this mineral makes it unsuitable as a jewelry stone.
Previously, phosphophyllite was found only in pegmatite at Hagendorf, Germany, as small transparent bluish-green crystals rarely over 1/4 inch in diameter. Recently, however, beautiful perfectly transparent, euhedral crystals as large as 2 inches by 1 inch by 3/4 inch have been found at Poopo, Bolivia. A few have been cut into splendid gems, but they are extremely rare and the Bolivian material disappeared quickly from the market. A 5.04-carat emerald-cut specimen is in the Smithsonian.
Phosphophyllite is brittle and tends to split along a perfect cleavage plane, but it is fairly tough otherwise. It is slightly heat sensitive, but dopping can be accomplished with stick shellac. It should be ground on a diamond/copper lap, and it polishes readily with Linde P on tin or wax. Crown angles should be 41° and pavilion angles 42°.