Mineralpedia Details for Esperite

Professor Esper Signius Larsen Jr., former American petrologist and mineralogist at Harvard University in Massachusetts, USA, is the namesake of the mineral Esperite. Esperite is a rare mineral that occurs at its type locality in the Parker shaft of the Franklin mine in New Jersey, USA and at El Dragon mine in Potosi, Bolivia. At the type locality it occurs within the metamorphosed stratiform zinc orebody. Esperite has a bright yellow fluorescence under short-wave ultraviolet light and has a kelly green cathodoluminescence.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/esperite.pdf

Formula

PbCa₂(ZnSiO₄)₃ 

Crystal System

Monoclinic 

Crystal Habit

Massive 

Cleavage

Indistinct, None, None 

Luster

Vitreous (Glassy) 

Color

white 

Streak

white 

Class

Monoclinic - Prismatic 

Fracture

Brittle 

Hardness

5 

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Mindat

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White-grey compact crystalline masses in Franklinite matrix with Zincite (orange) and Willemite (grey) - all are massive. Esperite is distinguished from the Willemite by fluorescing bright yellow. 1cm.