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.[4] 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.[5]

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.[6]

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.[5] 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. 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
  5. 5.0 5.1 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
  6. Weber, Julius (1974). The Formation of Minerals. Van Nostrand Reinhold Company. New York, London. pp. 78-80

External links