On the Occurrence of Petalite and Pneumatolytic Apatite in the Meldon Aplite, Okehampton, Devonshire1

W. F. P. McLintock
Curator, Museum of Practical Geology, London
1Communicated by permission of the Director, H.M. Geological Survey.

Summary: (1) Certain portions of the aplite have developed a soda-lithia phase characterized by the presence of petalite, a mineral not previously recorded from the British Isles, and its product of decomposition, montmorillonite.

(2) The Meldon aplite affords a good example of the pneumatolytic phenomena so characteristic of the granites of the West of England.

(3) Evidence is brought forward to show that apatite occurs as a pneumatolytic mineral in the aplite.

I desire to express my most cordial thanks to Dr. E. H Young of Okehampton, who placed his material and knowledge of the district entirely at my disposal for the purposes of this investigation.

Mineralogical Magazine; December 1923 v. 20; no. 103; p. 140-150; DOI: 10.1180/minmag.1923.020.103.03
© 1923, The Mineralogical Society
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