Boleite

Boleite is a complex halide mineral with formula: KPb₂₆Ag₉Cu₂₄(OH)₄₈Cl₆₂.^[3] 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]

Boleite
General
Category	Halide mineral
Formula	KPb26Ag9Cu24(OH)48Cl62
IMA symbol	Bol[1]
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
Other characteristics	Radioactive 0.36% (K)
References	[2][3][4]

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.^[3]

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.^[2]