Boleite

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]

Boleite
General
Category	Halide mineral
Formula (repeating unit)	KPb26Ag9Cu24(OH)48Cl62
Strunz classification	3.DB.15
Crystal system	Isometric
Crystal class	Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m)
Space group	Pm3m
Unit cell	a = 15.29 Å; Z = 1
Identification
Color	Deep Prussian blue to indigo
Crystal habit	Cubic crystals
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]

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. Handbook of Mineralogy
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. 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

• Gossner, Bernard (December 1928). "The Crystal form of Boleite" (PDF). The American Mineralogist. 13: 580–582.
• Cooper, Mark A.; Hawthorne, Frank C. (August 2000). "Boleite: Resolution of the Formula, KPb₂₆Ag₉Cu₂₄Cl₆₂(OH)₄₈". The Canadian Mineralogist. 38 (4): 801–808. doi:10.2113/gscanmin.38.4.801.
• Parker, Robert L. (1981). Rocks and Mineral Deposits. W.H. Freeman and Company. San Francisco. 343-422.
• Pirsson, Louis V. (1964). Rocks and Rock Minerals. John Wiley & Sons, Inc. New York, London. 34-56
• Williams, Peter A., Thomas, John H., Humphries, Alun, Samad, Abdul F. (1981). “Chemical Studies on the Stabilities of Boleite and Pseudoboleite”. Mineralogical Magazine v.44: 101-104 3
• link to cryptohalite