Esperite
(repeating unit)PbCa3Zn4(SiO4)4 IMA symbol Epr[1] Strunz classification 9.AB.15 Crystal system Monoclinic Crystal class Prismatic (2/m)
(same H-M symbol) Space group P21/m Identification Color White Crystal habit Typically massive Cleavage Distinct on [010] and [100] – poor on [101] Fracture Conchoidal, brittle Mohs scale hardness 5–5.5 Luster Vitreous Streak White Diaphaneity Subtranslucent to opaque Specific gravity 4.28–4.42 Optical properties Biaxial (−), 2V measured: 5° to 40° Refractive index nα = 1.762 nβ = 1.770 nγ = 1.774 Birefringence Max δ = 0.012 Other characteristics Brilliant yellow fluorescence under SW UV; kelly green cathodoluminescence. References [2][3][4] 
(same H-M symbol)
Esperite is a rare complex calcium lead zinc silicate (PbCa3Zn4(SiO4)4) related to beryllonite and trimerite that used to be called calcium larsenite. It was named in honor of Esper F. Larsen Jr. (1879–1961), petrologist of Harvard University.[clarification needed]
Esperite has a white, greasy appearance in daylight and is much prized for its brilliant yellow green fluorescence under shortwave ultraviolet light. It is found in association with calcite, franklinite, willemite, hardystonite and clinohedrite. It has also been found as prismatic crystals up to 1 mm in length at the El Dragon Mine, Potosi, Bolivia in association with allophane, chalcomenite, clinochalcomenite and barite.
References
Wikimedia Commons has media related to Esperite.
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ http://webmineral.com/data/Esperite.shtml Webmineral
- ^ http://www.mindat.org/min-1412.html Mindat
- ^ http://www.minsocam.org/msa/Handbook/Esperite.PDF Handbook of Mineralogy
- Mineral galleries
- Pete Dunn, Franklin and Sterling Hill, New Jersey: the world's most magnificent mineral deposits, part 3 p. 368 (1995)
- G. Grundmann, et al.: The El Dragon Mine, Potosi Bolivia, Mineralogical Record v.21 #2 p. 142 (1990)
- Anthony et al., Handbook of Mineralogy, Vol. 2 (silicates) part 1 p. 225 (1995)
Robbins, Manuel: Fluorescence Gems and Minerals under Ultraviolet Light Geoscience Press pp 50–51,243 (1994)
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