The Magnesium Aluminium Borosilicates: Kornerupine and Grandidierite

Duncan McKie
Department of Mineralogy and Petrology, Cambridge

Summary: A new occurrence of kornerupine in the skarn zone at Mautia Hill, Tanganyika, has yielded unit-cell dimensions a 16·100, b 13·767, c 6·735 Å, density 3·297, and composition Na0·01Mn0·01Ti0·02Mg3·69Fe0·37IIIAl6·36Si3·71B0·41O21·75(OH)0·25. The unit-cell clearly contains 88 anions rather than the 86 proposed previously. Grandidierite from Sakatelo, Madagasear, has unit-cell dimensions a 10·978, b 10·335, c 5·760 Å, space group Pna21 or Pnam, density 2·976, and composition Fe0·12IITi0·01Mg0·88Fe0·03IIIAl3·00Si1·00B0·97O9·00. The unit-cell contains 36 anions and the structure appears to involve A106 chains parallel to the c-axis.

Mineralogical Magazine; 1965 v. 34; no. 268; p. 346-357; DOI: 10.1180/minmag.1965.034.268.29
© 1965, The Mineralogical Society
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