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On larnite (calcium orthosilicate, a new mineral) and its associated minerals from the limestone contact-zone of Scawt Hill, Co. Antrim

Published online by Cambridge University Press:  14 March 2018

C. E. Tilley
C. E. Tilley*
Affiliation:
Department of Geology, University of Cambridge
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Extract

The contact-zone of Chalk and Tertiary dolerite at Scawt Hill, near Larne, Co. Antrim, consists of an assemblage of comparatively rare minerals, including a mineral of the composition Ca2SiO4 not previously recognized as a naturally occurring compound. In the assemblages of the contact-zone the chief minerals, apart from calcite, are spurrite, calcium orthosilieate (larnite), melilite (gehlenite), merwinite, spinel, perovskite, and wollastonite. Outside this contact-zone, the chalk consists almost wholly of calcium carbonate ; nearer the contact it is recrystallized to a granular mosaic of calcite of coarse texture, while at the immediate contact the chalk is completely transformed into an aggregate of new-formed silicates in varying proportions. A hybrid zone between the dolerite and the exogenous contact-rock is composed Of a coarsely crystalline rock built up essentially of titanaugite, melilite (humboldtilite), nepheline, wollastonite, perovskite, and various zeolites. An account of the melilite of this hybrid zone has already been given.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 22 , Issue 125 , June 1929 , pp. 77 - 86
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1929

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References

page 77 note 1 Tilley, C. E., Geol. Mag., 1929, vol. 66.CrossRefGoogle Scholar

page 78 note 1 Tilley, C. E., Min. Mag., 1928, vol. 21, p. xlviii, 1929, vol. 22, p. xxviiiGoogle Scholar; and Geol. Mag., 1927, vol. 64, p. 285.

page 78 note 2 Gough, G. C., Geol. Mag., 1907, dec. 5, vol. 4, p. 145.CrossRefGoogle Scholar

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page 79 note 1 Tilley, C. E., Geol. Mag., 1928, vol. 65, p. 372 Google Scholar. [Min. Abstr., vol. 4, p. 84.]

page 79 note 2 Foshag, W. F., Amer. Min., 1920, vol. 5, p. 80 Google Scholar; E. S. Larsen and W. F. Foshag, ibid., 1921, vol. 6, p. 143.

page 79 note 3 The Tasmanian mineral recorded as calcium orthosilicate by F. P. Paul (Tschermaks Min. Petr. Mitt., 1906, vol. 25, p. 309), and named shannonite (C. E. Tilley, Geol. Mag., 1927, vol. 64, p. 144) on the basis of Paul’s data, has since been shown to be monticellite (C. E. Tilley, Geol. Mag., 1928, vol. 65, p. 29). Rather than transfer the name ‘shannonite’ to the mineral now described, any further confusion will be avoided by adopting a new name. [See Min. Mag., 1928, vol. 21, p. 576.]

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