Chalcedony is the name used by gemologist for all cryptocrystalline quartz. Natural Chalcedony normally has no banding but because it is porous it is possible to dye this gem to colours not found naturally. Other well known gems that come in this group are carnelian and sard. This is normally found in either cabochon cut of sliced and polished similar to agate. It has a mohls hardness of 6.5-7