Larsenite
Larsenite is an IMA-recognized mineral species in the silicate class, with the chemical formula ZnPb(SiO₄).
It crystallizes in the orthorhombic crystal system (space group Pna2_1).
Key properties: Mohs hardness 3; specific gravity 5.9; Adamantine, pearly on platy surfaces luster; optically biaxial.
IMA symbol Lsn, grandfathered status — known before the IMA’s founding, named in 1928.
Found as a very rare secondary mineral in veins cutting and replacing coarse, massive willemite-franklinite ore in a metamorphosed stratiform zinc deposit (Franklin, New Jersey, USA).
It is found associated with Willemite, clinohedrite, esperite, hardystonite, hodgkinsonite, andradite, calcite, smithsonite, zincite, franklinite, roeblingite (Franklin, New Jersey, USA).
The name refers to Esper Signius Larsen, Jr. (1879–1961), American petrologist, Harvard University, Cambridge, Massachusetts, USA.