Apparent epitaxic overgrowth of richardsite on selective facets of primary wurtzite–sphalerite crystals. The image is published in an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( https://creativecommons.org/licenses/by/4.0/ ). — Photo: Luca Bindi and John A. Jaszczak · CC BY 4.0
Richardsite
Richardsite is an IMA-recognized mineral species in the sulfide class, with the chemical formula Zn₂CuGaS₄.
It crystallizes in the tetragonal crystal system (space group I-42m). It is a member of the Stannite structural group.
Key properties: Mohs hardness 3; specific gravity 4.278; Black streak; Metallic luster.
IMA symbol Ric, IMA status: approved, named in 2020.
On a single specimen reported to be from the Merelani gem mines.
It is found associated with Graphite, diopside, Ge-Ga-rich wurtzite.
The mineral was named to honor Dr. R. Peter Richards (b. 1943), retired water-quality researcher at Heidelberg College, Ohio, USA, and consulting editor of the journal Rocks & Minerals.