gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1978.042.321.04 Bazirite, BaZrSi3O9, a New Mineral from Rockall Island, Inverness-shire, Scotland Young B. R. Hawkes J. R. Merriman R. J. Styles M. T. Petrographical Department, Institute of Geological Sciences, Exhibition Road, London SW7 2DE 3 1978 42 321 35 40 22 4 1977 Copyright © 1978, The Mineralogical Society 1978 Summary

Bazirite, BaZrSi3O9, is one o f several late-stage interstitial minerals present in the aegirine-riebeckite granite of Rockall Island. Crystals are hexagonal, probably ¯6m2, colourless, chiefly as anhedral grains. Only forms noted {10¯10} and probably {10¯14}, cleavage {0001} and probably {10¯14}. ‘Low’ and ‘high’ titanium varieties with respective mean compositions: SiO2 39·71%, ZrO2 26·38%, BaO 33·69%, TiO2 0·17%, SnO2 0·06% and SiO2 39·59%, ZrO2 26·12%, BaO 34·12%, TiO2 0·51%, SnO2 0·11%. Low and high refractive index types exist; uniaxial positive with ω = 1·6751±0·0003. ɛ = 1·6850±0·0003 and ω = 1·6813±0·0003, ɛ = 1·691 (deduced); probably due to differences in titanium content. Fluorescence (2537 Å), moderately strong, pale whitish blue. Space group almost certainly P¯6c2. Cell dimensions: low R.I. variety, a = 6·7690±0·0005 Å, c = 10·020±0·001 Å; high R.I. variety, a = 6·7662± 0·0005 Å, c = 10·158±0·0010 Å. Strongest lines are 3·80 Å (100), 2·800 (100), 5·85 (35), 3·38 (35), Z = 2. Dcalc = 3·82. Related minerals, benitoite and pabstite.