Types of Chalcedony (Cryptocrystalline)
Other types of chalcedony, besides agate, include, Carnelian, Chrysoprase, Onyx, Thundereggs, Petrified Wood, and some include Aventurine. Chalcedony is found all over the world, including in each of the 50 states. Chalcedony has been used since the Bronze Age, and was especially common along the Mediterranean: in jewelry, beads, and even wax seals - because hot wax would not stick to it. The name of chalcedony comes from the town Chalkedon, which is in present-day Istanbul, and was formerly an ancient Greek village. Idar-Oberstein, a German town, became renowned in the 19th century as a major chalcedony and agate processing center, preparing and dying the stones for carving and jewelry making. Many chalcedonies, especially agate, take dye very well, and some are heat-treated, such as carnelian, to deepen the coloration.