Chemistry:Boleite

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Boleite
Boleite-rom51c.jpg
General
CategoryHalide mineral
Formula
(repeating unit)
KPb26Ag9Cu24(OH)48Cl62
Strunz classification3.DB.15
Crystal systemIsometric
Crystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space groupPm3m
Unit cella = 15.29 Å; Z = 1
Identification
ColorDeep Prussian blue to indigo
Crystal habitCubic crystals
Cleavage[001] perfect
FractureUneven
Mohs scale hardness3.0 – 3.5
|re|er}}Vitreous to pearly
StreakGreenish blue
DiaphaneityTranslucent
Specific gravity5.054
Optical propertiesIsotropic
Refractive indexn = 2.05
Other characteristicsRadioactive.svg Radioactive 0.36% (K)
References[1][2][3]

Boleite is a complex halide mineral with formula: KPb26Ag9Cu24(OH)48Cl62.[2] It was first described in 1891 as an oxychloride mineral. It is an isometric mineral which forms in deep-blue cubes. There are numerous minerals related to boleite, such as pseudoboleite, cumengite, and diaboleite, and these all have the same complex crystal structure.[5] They all contain bright-blue cubic forms and are formed in altered zones of lead and copper deposits, produced during the reaction of chloride bearing solutions with primary sulfide minerals.[6]

Physical properties

The external property of a boleite crystal structure indicates its cubic structure. It is classified under the isometric crystal class. Boleite has a perfect cleavage in the [001] direction, and has a very dark glossy blue color with a light greenish-blue color streak. Twinning is best shown in this mineral by notches along the interpenetrated angles, which results in a crystal habit of pseudocubic penetration twinning along three different angles perpendicular to one another. Boleite has cubes over half an inch on each side, which consist of pseudo-octahedral tetragonal dipyramids.[7]

Geologic occurrence

Boleite and atacamite from the Santa Rosa Mine, Noche Buena, Mazapil Municipality, Zacatecas, Mexico

Boleite was first collected as a very minor ore of silver, copper and lead at Boleo, Mexico.[6] Boleite was named after its place of discovery, El Boleo mine, on the Baja Peninsula, near Santa Rosalia, Mexico.[2]

Minerals associated with boleite include pseudoboleite, cumengeite, atacamite, anglesite, cerussite, phosgenite and gypsum at the type locality in Boleo, Mexico. In the Mammoth-St. Anthony mine of Arizona associated minerals include pseudoboleite, anglesite, cerussite, atacamite, paratacamite, leadhillite, paralaurionite, caledonite, phosgenite, matlockite and bideauxite.[1]

References

  1. 1.0 1.1 Handbook of Mineralogy
  2. 2.0 2.1 2.2 Mindat.org
  3. Webmineral data
  4. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode2021MinM...85..291W. https://www.cambridge.org/core/journals/mineralogical-magazine/article/imacnmnc-approved-mineral-symbols/62311F45ED37831D78603C6E6B25EE0A. 
  5. Martens, W., Williams, P.A., Frost, R.L. (2003) “Raman spectroscopy of the minerals boleite, cumengite, diaboleite and phosgenite – implications for the analysis of cosmetics of a antiquity”. Mineralogical Magazine. V.67: 103-111 1
  6. 6.0 6.1 Rouse, Roland C. (1973/01). “The Crystal Structure of boleite – A Mineral Containing Silver Atom Clusters”. Journal of Solid State Chemistry 6(1): 86-92 2
  7. Weber, Julius (1974). The Formation of Minerals. Van Nostrand Reinhold Company. New York, London. pp. 78-80

External links