Polarized light micrograph of a thin section of agate microcrystals. In the center of the image there is a cryptocrystalline quartz surrounded by microscopic intergrowth crystals in multi-colored banding. Quartz crystals can be seen in the outer area. 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: 27.8 x 41.7 mm (1.09 x 1.64 in)