Chemical Formula: Pb5(AsO4)3Cl

Chemical Name: Lead Chloroarsenate

Mineral Class: Arsenate

Mineral Notes: Mimetite is analogous to Pyromorphite with the arsenate (AsO4) 3-, replacing the phosphate anion (PO4) 3-. Although most properties are almost the same because of this, colour can usually be used to differentiate between the two, Mimetite being yellow and Pyromorphite being green.

Description: A grey matrix which contains a cavity lined with orange-brown Mimetite. The mineral mostly forms small spherical nodules, some of which are distorted to form flattened elliptical structures. A few of these are clustered together in an almost botryoidal formation. All have a strong sparkly luster, and some are transparent and quite gemmy. The host rock contains many other small crevices which are lined with more of these nodules and a few tiny crystals.

Location: El Potosi Mine, Chihuahua, Mexico.