Mimetite is a lead arsenate chloride mineral () which forms as a secondary mineral in lead deposits, usually by the oxidation of galena and arsenopyrite.
Mimetite forms a complete solid solution series with pyromorphite, with phosphate () substituting for arsenate (). The two minerals are almost identical in their properties and can be difficult to distinguish except by laboratory tests. Pyromorphite is the more common mineral at most locales.
Occurrences
Mimetite is found in association with lead and arsenic minerals, including pyromorphite, cerussite, hemimorphite, smithsonite, vanadinite, anglesite, pyrite, mottramite, willemite, and wulfenite.