gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1984.048.346.04 Malayaite and Tin-Bearing Garnet from a Skarn Gumble, NSW, Australia Mulholland I. R. * Department of Geology and Geophysics, University of Sydney, Sydney, NSW 2006, Australia

Now at: Esso Australia Ltd., Minerals Department, 127 Kent Street, Sydney, NSW 2000, Australia.

 3 1984 48 346 27 30 10 5 1982 25 4 1983 Copyright © 1984, The Mineralogical Society 1984 Abstract

Malayaite and tin-bearing garnet occur within a skarn assemblage at Gumble, NSW. A metasomatic origin is proposed for these minerals under conditions of T = 300-500°C Xco2 < 0.30 and fO2 = 10−18 to 10−30 bars. Malayaite has formed as a result of reaction between a metasomatic fluid rich in Sn, F, H2O and silica, and tin-bearing andradite and wollastonite. The main requirements for tin-bearing skarn formation appear to be an F-Sn-rich granite, an iron-rich skarn assemblage, and a relatively long cooling history.