Quartz crystals
Description:A photograph of an aggregate of quartz crystals sometimes referred to as rock crystals. These well-shaped hexagonal crystals are found in rock cavities throughout Connemara especially in the Galway Granites and the metamorphic rocks. Quartz is used in the manufacture of glass while coloured varieties (e.g. amethyst) are cut and polished as semiprecious stones.
Subject headings: Rocks -Minerals -Geology