Chalcedony is the term applied to most cryptocrystalline quartz. Cryptocrystalline means that the crystal structure is too small to be seen with a standard microscope. Chalcedony beads range from Semi-Transparent to Opaque in quality. They come in a variety of colors and can be color enhanced. Chalcedony and Agate are Quartz Varieties which may discolor or loose color when color treated by dye. Please allow for possible color change in any treated Chalcedony or Agate. The treatment may not be stable due to environmental factors such as heat, sun, or other adverse conditions on these gemstone varieties. Deposits of chalcedony form from solution and are often found lining cavities and crevices in caves or interiors of rocks. Agate is chalcedony that often forms as multi-colored bands. Onyx - Multi-colored chalcedony layered in parallel bands. Chrysoprase - An apple-green chalcedony colored by nickel-oxide. Carnelian - A red chalcedony colored by iron. Sard - A dark Brownish Red Chalcedony colored by iron. Jasper - A granular microcrystalline variety of quartz colored by elements or inclusions.