On the X-Ray Identification of Amblygonite and Montebrasite

A. A. Moss, E. E. Fejer and P. G. Embrey
Department of Mineralogy, British Museum (Natural History), London S.W. 7

Summary: Previous investigations have been confined to individual members or to small compositional ranges of the amblygonite-montebrasite series. The present study is a survey based on twenty-two specimens in the range Amb14Mon86 to Amb92Mon8 (1·8–11·8 % fluorine), and indicates that the fluorine content may be related both qualitatively and quantitatively to differences in the X-ray powder patterns. Fully indexed powder data to d = 1·68 Å and derived cell parameters are given for four members of the series. There is no evidence of a break in the continuity of the series. The first British occurrence of both amblygonite and montebrasite is reported from a pegmatite vein in aplite at Meldon, Okehampton, Devonshire.

Mineralogical Magazine; September 1969 v. 37; no. 287; p. 414-422; DOI: 10.1180/minmag.1969.037.287.15
© 1969, The Mineralogical Society
Mineralogical Society (www.minersoc.org)