Mineral Species: Mimetite var. Campyllite 

Chemical Formula: Pb5(AsO4)3Cl

Chemical Name: Lead Chloroarsenate

Mineral Class: Arsenate

Mineral Notes: Mimetite forms in secondary, weathered zones of lead ore deposits. It is very similar in composition to Pyromorphite, the difference being the substitution of the Arsenate ion by Phosphate. Campyllite is a variety of Mimetite characterised by barrel-shaped orange-yellow crystals. 

Description: Superbly formed crystals of orange-brown Campyllite. The largest is on the surface, whilst another large crystal nestles inside a matrix cavity. All have a very strong gemmy luster. The contrast against white Quartz is very striking and attractive.

Location: Dry Gill Mine, Caldbeck Fells, Cumbria, England.