Esperite
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.
| Esperite | |
|---|---|
 Esperite under ultraviolet light | |
| General | |
| Category | Silicate mineral |
| Formula (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] |
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
- 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)