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On the occurrence of Phenacite in Cornwall
Published online by Cambridge University Press: 14 March 2018
Extract
The mineral phenacite (beryllium ortho-silicate) has not previously been recorded from the British Isles. The following notes contain an account of its characters and mode of occurrence at five distinct localities in Cornwall. The occurrences are described in the order of their discovery.
During the early part of 1905, while examining the Cheesewring Quarry, in company with Mr. F. H. Butler, who on a previous visit had discovered bertrandite at this locality, I paid special attention to the diseovcry, if possible, of any other beryllium minerals. I was fortunate enough, after much searching, to find a specimen showing three small crystals that at once suggested the mineral phenacite ; a surmise which On examination proved correct.
- Type
- Research Article
- Information
- Mineralogical magazine and journal of the Mineralogical Society , Volume 16 , Issue 73 , May 1911 , pp. 55 - 62
- Copyright
- Copyright © The Mineralogical Society of Great Britain and Ireland 1911
References
Page 55 note 1 A crystal said to resemble Uralian phenacite, but possibly only beryl, was found by Dr. M. F. Heddle at Hillswicknsss Point, Shetland. It had rough faces, and was embedded in mica-slate (R. P. Greg and W. G. Lettsom, ‘Manual of the Mineralogy of Great Britain and Ireland,’ 1858, p. 478). This is not confirmed in Heddle's ‘Mineralogy of Scotland’, 1901.
Page 56 note 1 Mr. Hawkey the late manager, and Mr. Bennett the present manager of the quarry, have been most kind in affording me every facility in my search.
Page 56 note 2 Penfield, S. L. and Sperry, E. S., Amer. Journ. Sci., 1888, ser. 3, vol. xxxvi, p. 321 Google Scholar.
Page 56 note 3 Another crystal showed the game forms, but with only one face of developed. On this distorted crystal the goniometric determinations varied somewhat from the calculated values for phenacite; for instance, the three angles xx' gave 76° 58′, 76° 58′, 76° 49′ (instead of 75° 57′). On all the other Cornish crystals of phenacite which were measured normal angles were obtained. The development of vicinal faces thus seems to accompany the distorted growth of the crystals, as previously observed on phenacite from German East Africa (Mineralogical Magazine, 1906, vol. xiv, p. 178).—L. J. S.
Page 59 note 1 About the year 1856, Messrs. Pryor & Co, of Redruth, took over the old mines—Poldice, Wheal Unity, Wheal Gorland, and Wheal Maid, and consolidated them under the title of St. Day United Mines.
Page 59 note 2 Semmons, W., Journal Liverpool Geol. Assoc., 1892, vol. xii, p. 38.Google Scholar