Chalcedony, agates, jaspers, bloodstone, carnelian, onyx, and chrysoprase all make up the chalcedony gemstones.Quartz that is formed not of one single crystal but finely grained microcrystals is known as chalcedony. The variety of chalcedony is even greater than transparent quartz varieties because it includes cryptocrystalline quartz with patterns as well as a wide range of solid colours.
Agates are banded, bloodstone has red spots on a green ground and moss agate has a vegetal pattern. Blue lace agate is a pretty striated wedgwood blue and ivory. Jasper sometimes looks like a landscape painting.
Another staple of the jewellery industry is black onyx; chalcedony quartz which owes its even black colour to an ancient dying process that is still used today.|
Carnelian, another chalcedony valued in the ancient world, has a vivid brownish orange colour and clear translucency that makes it popular for signet rings and seals.
Carnelian is the birthstone for July.
Chrysoprase, a bright apple green translucent chalcedony, is the most valued. It was a particular favourite of Frederick the great of Prussia, who loved its vivid colour. It can be seen today decorating many buildings in beautiful Prague, including the Chapel of St. Wencelas.
Chalcedonies come in many different pastel colours - blue, lilac, aqua, white, yellow and grey - and have a waxy appearance. The blue toned chalcedonies are the most popular for jewellery.
They are porous and can be stained by metallic salts.