| Diaboleite | |
| Category: | Halide mineral |
| Formula: | Pb2CuCl2(OH)4 |
| Imasymbol: | Dbol[1] |
| Strunz: | 3.DB.05 |
| Dana: | 10.6.1.1 |
| System: | Tetragonal |
| Class: | Ditetragonal pyramidal (4mm) H-M symbol: (4mm) |
| Symmetry: | P4mm |
| Unit Cell: | a = 5.880, c = 5.500 Å, Z = 1 |
| Color: | Blue |
| Habit: | As square tabular crystals, thin plates, massive |
| Cleavage: | Perfect on |
| Fracture: | Conchoidal |
| Tenacity: | Brittle |
| Mohs: | 2.5 |
| Luster: | Adamantine, pearly on cleavages |
| Refractive: | nω = 1.980, nε = 1.850 |
| Opticalprop: | Uniaxial (−) |
| Birefringence: | δ = 0.130 |
| Absorption: | O > E, in thick fragments |
| Streak: | Pale blue |
| Density: | 5.41 to 5.43 g/cm3 |
| Solubility: | Completely soluble in nitric acid |
| Diaphaneity: | Transparent to translucent[2] |
| References: | [3] |
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 is deep blue in color and pale blue in transmitted light. The mineral occurs as tabular crystals up to 2abbr=onNaNabbr=on 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]
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 0.18mm 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 100C170C. At higher temperatures, the first stable mineral to form is cumengeite.[4]
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]
, 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]