Diaboleite
Blue-colored mineral
From Wikipedia, the free encyclopedia
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".[3] The mineral has since been found in a number of countries.
| Diaboleite | |
|---|---|
| |
| General | |
| Category | Halide mineral |
| Formula | Pb2CuCl2(OH)4 |
| IMA symbol | Dbol[1] |
| Strunz classification | 3.DB.05 |
| Dana classification | 10.6.1.1 |
| Crystal system | Tetragonal |
| Crystal class | Ditetragonal pyramidal (4mm) H-M symbol: (4mm) |
| Space group | P4mm |
| Unit cell | a = 5.880, c = 5.500 Å, Z = 1[2] |
| Identification | |
| Color | Blue |
| Crystal habit | As square tabular crystals, thin plates, massive |
| Cleavage | Perfect on {001} |
| Fracture | Conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 2.5 |
| Luster | Adamantine, pearly on cleavages[2] |
| Streak | Pale blue[2] |
| Diaphaneity | Transparent to translucent[2] |
| 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[2] |
| Solubility | Completely soluble in nitric acid |
| References | [3] |
Description
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.[2]
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.[2]
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.[4]
History
In 1923, diaboleite was discovered at Higher Pitts Mine in the Mendip Hills of Somerset, England,[3] and described by L. J. Spencer and E.D. Mountain.[5] 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".[6]
The mineral was grandfathered as a valid mineral by the International Mineralogical Association as it was described prior to 1959.[3]
Distribution
As of 2012[update], diaboleite has been found in Australia, Austria, Chile, France, Germany, Greece, Iran, Italy, Russia, South Africa, the UK and the US.[2][3] The type material is held at the Natural History Museum in London and the National Museum of Natural History in Washington, D.C.[2]
