Grossular Garnet (Grossular)

This specimen features grossular garnet, a calcium–aluminium silicate mineral belonging to the garnet group. The garnet occurs as granular to crystalline masses with characteristic yellow-green to olive-green tones, set within a pale, metamorphic host rock. Individual crystal faces are not well developed, which is typical of grossular formed in massive or granular habits rather than euhedral crystals. Grossular forms during metamorphism of calcium-rich rocks, such as limestone or marble, under conditions of elevated temperature and pressure. In the Tasman region, grossular is commonly associated with skarn and metamorphosed carbonate rocks, reflecting the complex tectonic and metamorphic history of northwest South Island.