Quartz

Quartz [SiO₂] Two specimens of quartz (var. amethyst; SiO₂), labeled a and b, consisting of pale lavender to medium violet, translucent crystals developed on quartz-rich and dark grey matrix. Crystals are closely intergrown, subhedral to euhedral, with vitreous lustre and well-developed rhombohedral terminations. Crystal size varies from fine to relatively coarse, with uneven violet colouration and locally visible colour zoning. The smaller specimen also displays colourless to milky quartz and minor yellow-orange staining adjacent to the dark host rock.