An association of hornblende and cummingtonite from Ringaringa, Stewart Island, New Zealand

Abstract

Summary Descriptions, with optical and chemical data, are given of hornblende and cummingtonite from an amphibolite exposed at the south end of Ringaringa beach, near Half Moon Bay, Stewart Island. The minerals are compared with similarly associated hornblende and cummingtonite described in recent years from Finland, and analyses are plotted to show the extent of the suggested miscibility gap between hornblendes and cummingtonites associated with them. The paragenesis of the hornblende and cummingtonite is briefly discussed. A short apepndix describes the method used in separating the amphiboles from the crushed rock for analysis.