Chrysoprase beads are the natural apple-green chalcedony colored by nickel-oxide. 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. The Chalcedony gem ranges from Semi-Transparent to Opaque in quality. It comes in a variety of colors and can be color enhanced. Deposits of chalcedony form from solution and are often found lining cavities and crevices in caves or interiors of rocks. Agate - (the most recognizable type of microcrystalline quartz) is chalcedony that often forms as multi-colored bands. Onyx - Multi-colored chalcedony layered in parallel bands. Heliotrope (Bloodstone) - A green chalcedony with red spots. 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.