Hostname: page-component-6bf8c574d5-w79xw Total loading time: 0 Render date: 2025-02-16T07:10:15.855Z Has data issue: false hasContentIssue false
  • English
  • Français

Note on an occurrence of bertrandite and beryl at the South Crofty mine, Cornwall1 (With Plate XXV.)

Published online by Cambridge University Press:  14 March 2018

James Phemister
James Phemister*
Affiliation:
Geological Survey and Museum, London
Get access Rights & Permissions [Opens in a new window]

Extract

Among a series of specimens collected by Mr. H. G. Dines from the South Crofty mine, Illogan, one was found to contain bertrandite and beryl. The specimen was obtained from the back of the 290-fathom level, east of Robinson's shaft, in the no. 1 lode, which hades north and at this position is 3 feet 10 inches wide. The location of the specimen was about 9 inches from the granite footwall. In hand-specimen the rock is a normal stanniferous veinstone composed of massive quartz tinted grey-green by disseminated chlorite and tourmaline and traversed by stripes of blackish ‘peach’ and white vein quartz which run parallel to the lode walls. Microscopically it is composed essentially of quartz, chlorite, and tourmaline, with subordinate orthoclase, fluorspar, and cassiterite, accessory apatite, and local bertrandite and beryl. In its texture there is evidence of an early formation of stanniferous chlorite-tourmaline peach with quartz-fluorspar gangue, which was subsequently fractured and, later, more or less completely healed by an accession of quartz, some redistribution of the earlier minerals having taken place at the same time. The place of bertrandite and beryl in this general scheme is discussed below (p. 576).

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 25 , Issue 170 , September 1940 , pp. 573 - 578
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1940

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Footnotes

1

Communicated by permission of the Director, Geological Survey and Museum.

References

page 574 note 1 Vogt, T., Bertrandit von Iveland im südlichen Norwegen. Zeits. Kryst. Min., 1911, vol. 50, pp. 6–13.Google Scholar

page 574 note 2 Bowman, H. L., On the occurrence of bertrandite at the Cheesewring quarry, near Liskeard, Cornwall. Min. Mag., 1911, vol. 16, pp. 47–50.CrossRefGoogle Scholar

page 575 note 1 Russell, A., Notes on the occurrence of bertrandite at some new localities in Cornwall. Min. Mag., 1913, vol. 17, pp. 15–21.CrossRefGoogle Scholar

page 576 note 1 Machatschki, F., Mineralogisehe Notizen. Der Beryll von Pisek und seine Zersetzungsprodukte . Zeits. Krist., 1926, vol. 63, p. 462. [M.A. 3–310.]Google Scholar

page 576 note 2 Pough, F. H., Bertrandite and epistilbite from Bedford, New York. Amer. Min., 1936, vol. 21, p. 265 [M.A. 6–362]Google Scholar; Ramdohr, P., Bertrandit yon Klein-Spitzkopje, Südwestafrika. Zentralbl. Min., Abt. A, 1936, p. 257 [M.A. 6–431]Google Scholar; Brandes, W., Das natürliche Vorkommen des Berylliums. Zeits. Prakt. Geol., 1933, voL 41, p. 35.Google Scholar

page 577 note 1 Penfield, S. L., Some observations on the beryllium minerals from Mt. Antero Colorado. Amer. Journ. Sci., 1890, vol. 40, pp. 489–490.Google Scholar