Diaboleite

Diaboleite

General
Category Halide mineral
Formula
(repeating unit)		 Pb2CuCl2(OH)4
Strunz classification 3.DB.05
Dana classification 10.6.1.1
Crystal symmetry Ditetragonal pyramidal
H-M symbol: (4mm)
Space group: P4mm
Unit cell a = 5.880 Å, c = 5.500 Å, Z=1[1]
Identification
Color Blue
Crystal habit As square tabular crystals, thin plates, massive
Crystal system Tetragonal
Cleavage Perfect on {001}
Fracture Conchoidal
Tenacity Brittle
Mohs scale hardness 2.5
Luster Adamantine, pearly on cleavages[1]
Streak Pale blue[1]
Diaphaneity Transparent to translucent[1]
Density 5.41 to 5.43 g/cm3
Optical properties Uniaxial (-)
Refractive index nω = 1.980, nε = 1.850
Birefringence δ = 0.130
Absorption spectra O > E, in thick fragments[1]
Solubility Completely soluble in nitric acid
References [2]

Diaboleite is a blue-colored mineral with formula Pb2CuCl2(OH)4. It was discovered in England in 1923 and named diaboleite, from the Greek word διά and boleite, meaning "distinct from boleite".[2] The mineral has since been found in a number of countries.

Description

Diaboleite crystal from a slag occurrence in the Laurium District, Attica, Greece (size: less than 1 mm)

Diaboleite is deep blue in color and pale blue in transmitted light. The mineral occurs as tabular crystals up to 2 cm (0.8 in) in size, as subparallel aggregates, or it has massive habit. Vicinal forms of the tabular crystals have a square or octagonal outline and rarely exhibit pyramidal hemihedralism.[1]

Formation

Diaboleite occurs in manganese oxide ores, as a secondary mineral in lead and copper oxide ores, and in seawater-exposed slag. Diaboleite has been found in association with atacamite, boleite, caledonite, cerussite, chloroxiphite, hydrocerussite, leadhillite, mendipite, paratacamite, phosgenite, and wherryite.[1]

A study in 1986 synthesized diaboleite crystals up to 0.18 mm (0.0071 in) in size using two different methods. The study demonstrated that diaboleite is a low-temperature phase, that is stable under hydrothermal conditions at temperatures less than 100 to 170 °C (212 to 338 °F). At higher temperatures, the first stable mineral to form is cumengeite.[3]

History

In 1923, diaboleite was discovered at Higher Pitts Mine in the Mendip Hills of Somerset, England,[2] and described by L. J. Spencer and E.D. Mountain.[4] The study of the similar mineral boleite was perplexing at the time and this new mineral only compounded the difficulty. As insufficient material was available for a full investigation, Spencer and Mountain named it diaboleite, meaning "distinct from boleite", out of "desperation".[5]

The mineral was grandfathered as a valid mineral by the International Mineralogical Association as it was described prior to 1959.[2]

Distribution

As of 2012, diaboleite has been found in Australia, Austria, Chile, France, Germany, Greece, Iran, Italy, Russia, South Africa, the UK and the US.[1][2] The type material is held at the Natural History Museum in London and the National Museum of Natural History in Washington, D.C.[1]

References

Citations
  1. 1 2 3 4 5 6 7 8 9 "Diaboleite" (PDF). Handbook of Mineralogy. Retrieved June 11, 2012.
  2. 1 2 3 4 5 "Diaboleite". Mindat. Retrieved June 11, 2012.
  3. ↑ Winchell, p. 934.
  4. ↑ Spencer, p. 78.
  5. ↑ Spencer, p. 79.
Bibliography

Further reading

External links

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