Formula: PbAl3(PO4)(PO3OH)(OH)6


Colour: Light blue, gray-white, yellow-gray, yellow, yellow-brown, red-brown, greenish, bluish, dark blue-gray;

Lustre: Resinous, Dull

Hardness: 4 – 5

Specific Gravity: 4.014

Crystal System: Trigonal

Member of: Plumbogummite Group > Alunite Supergroup

Name: Named in 1819 by François Pierre Nicolas Gillet de Laumont from the Latin “plumbum” for lead, and “gummi” for gum, in allusion to its lead content and appearance at times as drops or coatings of gum.

Type Locality: Huelgoat, Châteaulin, Finistère, Brittany – France

The lead analogue of crandallite and goyazite, and the phosphate analogue of philipsbornite. Compare also the chemically similar hinsdalite with which it forms a complete solid-solution series. A relatively common secondary lead aluminium phosphate mineral.