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.[clarification needed]

Esperite
Esperite under UV light.jpg
Esperite under ultraviolet light
General
CategorySilicate mineral
Formula
(repeating unit)		PbCa3Zn4(SiO4)4
Strunz classification9.AB.15
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/m
Identification
ColorWhite
Crystal habitTypically massive
CleavageDistinct on [010] and [100] - poor on [101]
FractureConchoidal, brittle
Mohs scale hardness5 - 5.5
LusterVitreous
StreakWhite
DiaphaneitySubtranslucent to opaque
Specific gravity4.28 - 4.42
Optical propertiesBiaxial (-), 2V measured: 5° to 40°
Refractive indexnα = 1.762 nβ = 1.770 nγ = 1.774
BirefringenceMax δ = 0.012
Other characteristicsBrilliant yellow fluorescence under SW UV; kelly green cathodoluminescence.
References[1][2][3]

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.

This article uses material from the Wikipedia article
 Metasyntactic variable, which is released under the 
Creative Commons
Attribution-ShareAlike 3.0 Unported License

Note

This article uses material from the Wikipedia article
 Metasyntactic variable, which is released under the 
Creative Commons
Attribution-ShareAlike 3.0 Unported License.