Birchite
Birchite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Cd₂Cu₂(PO₄)₂(SO₄)·5H₂O.
It crystallizes in the orthorhombic crystal system (space group Pnma).
Key properties: Mohs hardness 3.5–4; specific gravity 3.61; White streak; Vitreous luster; optically biaxial.
IMA symbol Bc, IMA status: approved, named in 2006.
A late-stage supergene mineral formed in small cavities and thin seams as part of a suite of secondary phosphate minerals under low-temperature condition in an intensely deformed and metamorphosed stratiform base metal deposit of submarine.
It is found associated with Hinsdalite-plumbogummite, cerussite, anglesite, pyromorphite, libethenite, sampleite.
The mineral was named to honor William D. Birch, Senior Curator of Geosciences, Museum Victoria, Australia, for his contributions to Australian geological sciences.