Diaboleite
| Diaboleite | |
|---|---|
Diaboleite at the American Museum of Natural History, in New York City
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| General | |
| Category | Halide mineral |
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Formula (repeating unit) |
Pb2CuCl2(OH)4 |
| 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 |
| 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 |
| Streak | Pale blue |
| Diaphaneity | Transparent to translucent |
| 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 |
| Solubility | Completely soluble in nitric acid |
| References | |
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". The mineral has since been found in a number of countries.
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. forms of the tabular crystals have a square or octagonal outline and rarely exhibit pyramidal .
Diaboleite occurs in manganese oxide ores, as a secondary mineral in and 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.
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.
In 1923, diaboleite was discovered at Higher Pitts Mine in the Mendip Hills of Somerset, England, and described by L. J. Spencer and E.D. Mountain. 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".
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Wikipedia