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The occurrence of a gold-bearing pegmatite on Dartmoor

Published online by Cambridge University Press:  14 March 2018

A. Brammall  and
H. F. Harwood
A. Brammall
Affiliation:
Imperial College of Science and Technology, London
H. F. Harwood
Affiliation:
Imperial College of Science and Technology, London
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Extract

A Remarkable pegmatite occurring on Bittleford Down (Wind Tor), near Widecombe, is described in the Survey Memoir as a veinrock containing (a) abundant hornblende, a mineral not previously found in any of the post-Carboniferous granites of the west of England, (b) much sphene, (c) porphyritic crystals of oligoclase, and (d) quartz crowded with fluid inclusions.

This rock is of peculiar interest in other respects. Its complete freedom from biotite and its high content of felspar (oligoclase dominant over orthoclase) imply considerable deviation in bulk composition from the normal Dartmoor granite. Moreover, its accessory minerals include both gold and silver.

Considered broadly as a coarse-grained felsic type, its position in the list of variants from the normal granite is shared by a still more felsic rock with which it is closely associated in the field.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 20 , Issue 105 , June 1924 , pp. 201 - 211
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1924

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References

Page 201 note 1 The Geology of Dartmoor, Mem. Geol. Survey, 1912, p. 41.

Page 202 note 1 Brammall, A. and Harwood, H. F., The Dartmoor granite : its mineralogy, structure, and petrology. Min. Mag., 1923 (June), vol. 20, pp. 41–42 CrossRefGoogle Scholar.

Page 202 note 2 Ibid., p. 53.

Page 203 note 1 K. Brammall and H. F. Harwood, loc. cit., 1923 (June), p. 53.

Page 203 note 2 Ibid., 1923 (March) p. 23.

Page 204 note 1 A. Brammall and H. F. Harwood, loc. cit., 1923 (March), p. 22.

Page 205 note 1 A. Brammall and H. F. Harwood, loc. cit, 1923 (March), pp. 27-81.

Page 205 note 2 Ibid., pp. 20-26.

Page 206 note 1 A. Brammall and H. F. Harwood, loc. cit, 1923 (June), pp. 40-42

Page 210 note 1 Greg, R. P. and Lettsom, W. G., Mineralogy of Great Britain and Ireland, 1858, p. 237 Google Scholar.

Page 210 note 2 Gordon, W. T., Nature, London, 1922, vol. 109, p. 583 CrossRefGoogle Scholar.

Page 210 note 3 Lacroix, A., Minéralogie de Madagascar, 1922, vol. 1, p. 163 Google Scholar ; vol. 2, p. 26.

Page 210 note 4 Merrill, G. P., Amer. Journ. Sci., 1896, ser. 4, vol. 1, p. 309 CrossRefGoogle Scholar (Abstr. Min. Mag., vol. 11, p. 227). Blake, W. P., Trans. Amer. Inst. Min. Eng., 1897, vol. 26, p. 292 Google Scholar.