SUGILITE IN MANGANESE SILICATE ROCKS FROM THE HOSKINS MINE AND WOODS MINE, NEW-SOUTH-WALES, AUSTRALIA

Sugilite relatively rich in manganese has been found at two new locali ties, the Hoskins and Woods mines in New South Wales, Australia. The o ccurrences are in manganese-rich silicate rocks of middle to upper gre enschist facies (Hoskins mine) and hornblende hornfels facies (Woods m ine). Coexisting minerals are members of the namansilite-aegirine and pectolite-serandite series, Mn-rich alkali amphiboles, alkali feldspar , braunite, rhodonite, tephroite, albite, microcline, norrishite, with erite, manganoan calcite, quartz, and several unidentified minerals. W oods mine sugilite is colour-zoned with pale mauve cores and colourles s rims, whereas Hoskins mine sugilite is only weakly colour-zoned and pink to mauve. Within single samples, the chemical compositions of sug ilite from both localities show wide ranges in Al contents and less va riable ranges of Fe and Mn, similar to trends in sugilite from other l ocalities. The refractive indices and cell dimensions tend to show sys tematic increases progressing from Al-rich to Fe-Mn-rich. The formatio n of the sugilite is controlled by the high alkali (especially Li) and manganese contents of the country rock, reflected in the occurrences of coexisting high alkali- and manganese-bearing minerals, and by high f(O2) conditions