Mica

Crockett, R.N.. 1975 Mica. London, UK, HMSO, 27pp. (Mineral Dossier No. 15)

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Abstract/Summary

Mica is the collective name for various complex hydrous aluminium silicate minerals that are characterised by a perfect basal cleavage. This cleavage enables the natural crystals to be split into very thin plates. Among the many varieties of mica, muscovite has major industrial importance and is the principal subject of this dossier. The main classes of mica utilised for industrial purposes are sheet, scrap and flake mica. Ground mica is generally produced from scrap or flake mica. The term 'manufactured mica' is usually taken to refer to synthetic products incorporating mica such as micanite, mica paper and glass-bonded mica. Mica commonly occurs in igneous rocks, mainly of granitic composition, and in gneissic and schistose metamorphic rocks. Commercial quantities of mica are extracted from mica-bearing pegmatites in various parts of the world. In Scotland mica pegmatites occur in the Highland Region, principally in the former counties of Inverness and Ross and Cromarty. These are small, disconnected and lenticular bodies. Although some were worked during the Second World War, their present economic potential is doubtful. While mica suitable for grinding has been produced from mica schists in the United States, attempts to start similar operations in the United Kingdom have not as yet proved successful. The uses of mica are based upon a unique combination of physical, chemical and electrical properties. Sheet mica is mainly used by the electrical and electronic industries, although wet and dry ground mica find a wider range of industrial uses. Owing to the geological nature of the pegmatite deposits from which sheet mica is obtained, mining is usually on a small scale and not highly mechanised. In Britain flake mica was, until 1975, extracted as a by-product from china clay working at Lee Moor, Devon. A number of companies produce ground mica from imported waste or from domestic flake mica. There are no materials that can totally replace mica in all its applications. However, for applications such as stove windows, sparking plugs and radio condensers, substitution is possible. Reconstituted mica has been found particularly suitable for electrical insulation. Synthetic mica is a potential substitute for natural sheet mica but to date it has been found difficult to grow large crystals economically and in substantial amounts.

Item Type:	Publication - Report
Programmes:	BGS Programmes > Economic Minerals
Funders/Sponsors:	Institute of Geological Sciences
Additional Keywords:	Mineral, Mica
NORA Subject Terms:	Earth Sciences
Date made live:	05 Aug 2025 12:31 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/539966

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