Amethystine and clear crystalline quartz infills fractures and cavities in quartzite of the Belair Subgroup of Proterozoic age, near Fullerville in the Mid-North of South Australia. The quartz crystals range in colour from milky to clear, through light and dark purple, to nearly black. Crystal form is poor due to intergrowth within the veins and mild deformation during crystal growth. Most of the amethystine quartz is merely of specimen value, with only minor amounts of semi-precious material being available.