Geochemical study of idocrase and description of a skarn at Rameka creek, Northwest Nelson

Abstract

Hydrothermal synthesis of idocrase of various compositions has been accomplished from prepared oxide mixes and glasses, and also from decomposition products and a glass made from natural idocrase crystals. The mineral has a wide field of crystallisation but it decreases in size as the iron content of the starting material is increased at the expense of magnesium. Rare earth (Y3+) and copper varieties may have been synthesised. Growth of idocrase on a seed plate was not achieved despite the use of many methods and nutrient materials. A skarn in northwest Nelson is described, and its mineral zones compare closely with those of other localities. Of the three variables, PH2O temperature and composition, the last appears to be the most important in determining whether or not idocrase will crystallise.