Abstract
An extensive search for winchite [CaNaMg4AlSi8O22(OH)2] by microprobe anlyses of violet amphiboles obtained from the type locality has failed to identify any sodic calcic amphiboles. In particular, none is near to either the original or the theoretical end-member composition of winchite. The violet amphiboles are generally magnesio-arfvedsonite to magnesio-riebeckite, sometimes manganoan and titanian, but always alkali amphiboles. In addition, the Mn-rich amphiboles have C-group totals significantly lower than the 5.00 expected in the ideal amphibole formula. Colorless tremolite is present in some of the violet amphibole-bearing rocks. We suggest, but have not conclusively proved, that the original analysis of winchite was in error.
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