Museo di storia naturale (Florence) - Mineralogy section — Photo: Sailko · CC BY-SA 3.0
Esperite
A rare calcium-lead-zinc silicate related to beryllonite, once called calcium larsenite.
Intro adapted from Wikipedia (CC BY-SA).
Esperite is an IMA-recognized mineral species in the silicate class, with the chemical formula PbCa₂(ZnSiO₄)₃.
It crystallizes in the monoclinic crystal system (space group P2_1/n). It is a member of the Beryllonite structural group.
Key properties: Mohs hardness 4.5; specific gravity 4.28–4.42; typically yellow; white streak; Dull to slightly greasy luster; refractive index 1.769; optically biaxial.
IMA symbol Epr, IMA status: approved, named in 1964.
Found in a metamorphosed stratiform zinc orebody.
It is found associated with Willemite, zincite, hardystonite, glaucochroite, andradite, franklinite, clinohedrite, leucophoenicite, larsenite, copper.
The mineral was named to honor Professor Esper Signius Larsen, Jr. (1879–1961), American petrologist and mineralogist, Harvard University, Cambridge, Massachusetts, USA.
Collections: Collector Favorites, Rare & Remarkable, Fluorescent & Glowing.