Polarized light micrograph of a thin section of agate microcrystals. In the center and at the bottom of the image there are microscopic crystal intergrowths in multi-colored banding. At the top there are quartz crystals with quartz microcrystals on their upper edge. The agate is a semi-precious gemstone variety of chalcedony. It is a microcrystalline silica with a chemical composition of SiO2 (silicon dioxide), and some of its other physical properties are those of quartz. Its uses are: hardstone carving, decorative arts, jewellery, crafts and industry. Field of view size: 22.3 x 33.4 mm (0.88 x 1.32 in)