Esperite

nesosilicate

willemite

Formula: PbCa2(ZnSiO4)3
Nesosilicate
Specific gravity: 4.28 to 4.42
Hardness: 5
Streak: White
Colour: White, off-white, pale tan; may be orange or light brown due to fine-grained inclusions of andradite or zincite
Solubility: Readily soluble in nitric acid (AM 13.334-340)
Environments:

Metamorphic environments

Esperite occurs in metamorphosed stratiform zinc deposits, associated with willemite, zincite, hardystonite, glaucochroite, andradite, franklinite, clinohedrite, leucophoenicite, larsenite and native copper (Webmin).

At the type locality, the Parker Shaft, Franklin Mine, Franklin, New Jersey, USA, esperite occurs in typical Franklin ore (comprising willemite, zincite, franklinite and calcite) with hardystonite and clinohedrite. It is often found as pseudomorphs after hardystonite, (Mindat) and more rarely with native copper and glaucochroite. A sample has been reported which contains esperite, andradite, willemite and traces of leucophoenicite (AM 50.1170-1178).

Common impurities: Fe,Mn,Mg

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