Esperite

Esperite is named after Esper Signius Larsen, Jr., Professor of Geology, Harvard University.

Esperite has a white, greasy appearance in daylight and shows brilliant yellow green fluorescence under shortwave ultraviolet light.
General Information
Chemical Formula
PbCa
 
3
Zn
 
4
(SiO
 
4
)
 
4
Anthony et al, Handbook of mineralogy (2001)
Photos of natural/un-cut material from mindat.org
Physical Properties of Esperite
Mohs Hardness5 to 5.5
Anthony et al, Handbook of mineralogy (2001)
Specific Gravity4.28 to 4.42
Anthony et al, Handbook of mineralogy (2001)
Cleavage QualityDistinct,Poor
Anthony et al, Handbook of mineralogy (2001)
FractureConchoidal
Anthony et al, Handbook of mineralogy (2001)
Light SensitivityDarkens on exposure to light
Anthony et al, Handbook of mineralogy (2001)
Optical Properties of Esperite
Refractive Index1.760 to 1.774
Anthony et al, Handbook of mineralogy (2001)
Optical CharacterBiaxial/-
Anthony et al, Handbook of mineralogy (2001)
Colour
Colour (General)White
Anthony et al, Handbook of mineralogy (2001)
TransparencyOpaque
Anthony et al, Handbook of mineralogy (2001) Opaque, transparent in small grains.
LustreGreasy,Dull (Earthy)
Anthony et al, Handbook of mineralogy (2001) Dull to slightly greasy.
Fluorescence & other light emissions
Fluorescence (Short Wave UV)Brilliant yellow fluorescence
Anthony et al, Handbook of mineralogy (2001)
Crystallography of Esperite
Crystal SystemMonoclinic
Anthony et al, Handbook of mineralogy (2001)
HabitGranular aggregates, massive, to 9 cm.
Anthony et al, Handbook of mineralogy (2001)
Geological Environment
Where found:In a metamorphosed stratiform zinc orebody.
Anthony et al, Handbook of mineralogy (2001)
Further Information
Mineral information:Esperite information at mindat.org
Significant Gem Localities
USA
 
  • New Jersey
    • Sussex Co.
      • Franklin Mining District
        • Franklin
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