Boleite

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Boleite
Boleite.jpg
General
Category Halide mineral
Formula
(repeating unit)
KPb26Ag9Cu24(OH)48Cl62
Strunz classification 03.DB.15
Crystal system Isometric
Unit cell a = 15.29 Å; Z = 1
Identification
Color Deep Prussian blue to indigo
Crystal habit Cubic crystals
Crystal symmetry Cubic (4/m 3 2/m) hexoctahedral
Cleavage [001] perfect
Fracture Uneven
Mohs scale hardness 3.0 – 3.5
Luster Vitreous to pearly
Streak Greenish blue
Diaphaneity Translucent
Specific gravity 5.054
Optical properties Isotropic
Refractive index n = 2.05
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[edit]

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[edit]

Boleite and atacamite from the Boleo mine (size: 5.2 x 4.2 x 3.0 cm)

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[edit]

  1. ^ a b Handbook of Mineralogy
  2. ^ a b c 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. ^ a b 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[edit]