Bismoclite is a

bismuth Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs ...

oxohalide In chemistry, molecular oxohalides (oxyhalides) are a group of chemical compounds in which both oxygen and halogen atoms are attached to another chemical element A in a single molecule. They have the general formula , where X = fluorine (F), ch ...

mineral with formula BiOCl. It is the naturally occurring form of

bismuth oxychloride Bismuth oxychloride is an inorganic compound of bismuth with the formula Bi O Cl. It is a lustrous white solid used since antiquity, notably in ancient Egypt. Light wave interference from its plate-like structure gives a pearly iridescent light ...

. The name was derived from its chemical constituents. It is a secondary bismuth mineral first thought to be composed of bismuthyl ions (BiO⁺) and chloride anions, however, the existence of the diatomic bismuthyl ion is doubtful. It is a member of the matlockite group. It was first described in 1935 from alluvium near bismuth-bearing pegmatites in South Africa. It has been found in association with

granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies under ...

pegmatite and in

greisen Greisen is a highly altered granitic rock or pegmatite, usually composed predominantly of quartz and micas (mostly muscovite). Greisen is formed by self-generated alteration of a granite and is a class of moderate- to high-temperature magmatic-hy ...

. Associated minerals include

bismutite Bismutite or bismuthite is a bismuth carbonate mineral with formula Bi2(CO3)O2 (bismuth subcarbonate). Bismutite occurs as an oxidation product of other bismuth minerals such as bismuthinite and native bismuth in hydrothermal veins and pegmatites. ...

, mica,

jarosite Jarosite is a basic hydrous sulfate of potassium and ferric iron (Fe-III) with a chemical formula of KFe3(SO4)2(OH)6. This sulfate mineral is formed in ore deposits by the oxidation of iron sulfides. Jarosite is often produced as a byproduct du ...

, alunite,

cerussite Cerussite (also known as lead carbonate or white lead ore) is a mineral consisting of lead carbonate (PbCO3), and is an important ore of lead. The name is from the Latin ''cerussa'', white lead. ''Cerussa nativa'' was mentioned by Conrad Gessner ...

atacamite Atacamite is a copper halide mineral: a copper(II) chloride hydroxide with formula Cu2Cl(OH)3. It was first described for deposits in the Atacama Desert of Chile in 1801 by D. de Fallizen. The Atacama Desert is also the namesake of the mineral. ...

, connellite. Occurrences include the type locality at Jackals Water, SW of

Prieska Prieska is a town on the south bank of the Orange River, in the province of the Northern Cape, in western South Africa. It is located on the southern bank of the Orange River, 130 km north-west of Britstown and 75 km south-east of Mary ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...

; Bygoo, Australia; the Tintic district in the

East Tintic Mountains The East Tintic Mountains are a mountain range in central Juab, Utah, and Tooele counties in Utah, United States on the east margin of the Great Basin just west of the Wasatch Front about south-southeast of Salt Lake City. The community of Eur ...

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

; and from

Dalbeattie Dalbeattie (, sco, Dawbeattie, gd, Dail Bheithe meaning 'haugh of the birch' or ''Dail'' ''bhàite'' 'drowned (''i.e.'' liable to flood) haugh') is a town in the historical county of Kirkcudbrightshire in Dumfries and Galloway, Scotland. Dalbe ...

Scotland Scotland (, ) is a Countries of the United Kingdom, country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a Anglo-Scottish border, border with England to the southeast ...

Crystal structure

The crystal structure of bismoclite was found to be composed of linked

decahedron In geometry, a decahedron is a polyhedron with ten faces. There are 32300 topologically distinct decahedra, and none are regular, so this name does not identify a specific type of polyhedron except for the number of faces. Some decahedra have ...

s, specifically a

square antiprism In geometry, the square antiprism is the second in an infinite family of antiprisms formed by an even-numbered sequence of triangle sides closed by two polygon caps. It is also known as an ''anticube''. If all its faces are regular, it is a sem ...

. These decahedrons consist of 2 squares with sides of 3.487 Å (O-O-O-O and Cl-Cl-Cl-Cl) connected by 8 isosceles triangles (O-Cl-O and Cl-O-Cl), with a bismuth atom at the centre. The Bi-O distances and Bi-Cl distances are 2.316 Å and 3.059 Å, respectively. The O-Cl distances in the triangles are 3.249 Å. The decahedrons are linked to each other through shared O-Cl sides.

References

Bismuth minerals Oxide minerals Halide minerals Tetragonal minerals Minerals in space group 129 {{halide-mineral-stub