Chalcedony is named after its classic source, Chalcedon, a Roman province of Bithynia located in present day Turkey.
History of Chalcedony
Chalcedony features in Jewish, Christian, Islamic and Buddhist religious traditions. Chalcedony was a big part of the ancient's gemstone repertoire, playing an important role in Mesopotamian (modern-day Iraq), Hittite (modern-day Turkey), Egyptian and Greek civilisations. To put its heritage into context, Agate (banded Chalcedony) beads dating back to 7000 BC have been excavated in Turkey. The Romans particularly prized Chalcedony, they used Chalcedonies as magic amulets, seals, signets, cameos (a gem carved in positive relief) and intaglios (a gem carved in negative relief), setting them in rings, brooches, bracelets and necklaces. Continuously mined since Roman times, fine translucent Blue Chalcedony from Turkey, also known as Blue Turk Chalcedony, remains highly regarded.
Composition of Chalcedony
Despite being a gem and a family name, Chalcedony is also a sub-group within the family that covers its uniformly coloured members. Its multicoloured varieties are all under the Agate umbrella. Popular Chalcedony Quartz gemstones include Agate, Aventurine, Bloodstone, Carnelian, Chrysoprase, Jasper and Onyx.
Properties of Chalcedony
Chalcedony is typically translucent to opaque, coming in a huge array of colours including shades of black, blue, brown, green, grey, orange, pink, red, white, yellow, and combinations thereof. For Chalcedony colour is the most important factor, so is the presence of banding, mottling and spots in some varieties. Banded, mottled or spotted Chalcedony is assessed by judging the beauty and intensity of the colours and patterns present. Usually polished as cabochons, Chalcedony is also frequently used in carvings, cameos and intaglios.
Sources of Chalcedony
Chalcedony is quite common and can be found in many countries including Brazil, United States, Mexico and Russia.