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What is plinthite?

Published online by Cambridge University Press:  14 March 2018

Jessie M. Sweet*
Affiliation:
Dept. of Mineralogy, British Museum (Natural History)

Summary

Many specimens of plinthite, a species described from Co. Antrim by T. Thomson in 1836 and later from Skye by M. F. Heddle, prove to be mixtures of zeolites and hematite. Both original analyses are those of a ferruginous clay (a mixture of hematite, kaolinite, and montmorillonite). The type specimen (Thomson Collection) is a red clay in the montmorillonite group intimately mixed with hematite and a little analcime.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1960

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References

page 455 note 1 T. Thomson, Outlines of Mineralogy, Geology, and Mineral Analysis, 1836, p. 323.

page 455 note 2 Heddle, M. F., Min. Mag., 1882, vol. 5, p. 26.Google Scholar

page 455 note 3 Heddle, M. F., Min. Mag., 1883, vol. 5, p. 117 Google Scholar.

page 455 note 4 See p. 457, below.

page 456 note 1 Allan-Greg Colln.: obtained by R. P. Greg between 1848 and 1851.

page 456 note 2 No. 02-161 abw. Presented by Major A. J. Fleraing, 1901 (probably collection of Professor John Fleming (1785-1857) of AIcerdeen).

page 457 note 1 Heddle, M. F., Min. Mag., 1883, vol. 5, p. 118.Google Scholar

page 457 note 2 Allan-Greg Colln.; obtained by R. P. Greg between 1848 and 1851.

page 458 note 1 Heddle also noticed at The Quirang and even more abundantly at The Storr (Min. Mat., 1883, vol. 5, p. 119) a variety of thomsonite that has been called 'rock-soap'. It is, however, rough and not soapy in texture, and in appearance rather like kaolinite. The present writer found similar material near Uig, which when fresh was sugary and granular in appearance but on drying became more hard and compact. It was found to consist of a mixture of fine-grained analcime and thomsonite (B.M. 1959, 567) or just analcime (B.M. 1959, 568).

page 458 note 2 Heddle, M. F., Min. Mag., 1882, vol. 5, p. 24 Google Scholar.