Genthelvite and Bertrandite from the Cairngorm Mountains, Scotland

W. C. Morgan
Department of Geology, The University, Newcastle upon Tyne

Summary: A zinc-rich helvine (genthelvite) has been found with bertrandite in miarolitic cavities in adamellite at Coire an Lochain in the Cairngorm Mountains. The genthelvite occurs as green or brown tetrahedral crystals of sp. gr 3·58±0·01. It is isotropic, n 1·742±0·003, a 8·133±0·005 Å. Bertrandite crystals are pale brown with sp. gr. 2·60±0·01; biaxial negative with 2V 75°, and α 1·590, β 1·603, γ 1·613, all ±0·003.

Mineralogical Magazine; March 1967 v. 36; no. 277; p. 60-63; DOI: 10.1180/minmag.1967.036.277.08
© 1967, The Mineralogical Society
Mineralogical Society (