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Formula: PbCa2(ZnSiO4)3
Nesosilicate (insular SiO4 groups)
Crystal System: Monoclinic
Specific gravity: 4.28 to 4.42 measured, 4.25 calculated
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)
Common impurities: Fe,Mn,Mg
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).
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