Chalcedonies are uniquely beautiful gemstones that connect us with a bygone era.
The Romans greatly prized all varieties of Chalcedony
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.
Source of Chalcedony
Chalcedony is quite common and can be found in many countries including Brazil, United States, Mexico and Russia.
Crazy Lace Agate
The banded form of Chalcedony, Agate's name comes from the river Achates (now Dirillo) in Sicily. Agate's banded patterns are caused by the oxidisation of manganese, iron and other minerals. Coming in a huge array of colours and an infinite number of patterns, Agate's numerous varieties have a plethora of descriptive prefixes.
Aventurine is typically a green Chalcedony whose small inclusions of mica, goethite, hematite and fuschite create a sparking effect aptly called 'aventurescence'.
Carnelian is the orange to red variety of Chalcedony named from the Latin 'carneus' (made of flesh) due to its colouration. The oranges and reds of Carnelian are caused by iron oxide. Carnelian is also a gem with deep religious and spiritual connections, featuring in Egyptian, Tibetan Buddhist and Christian traditions. A gemstone revered by Muslims, Carnelian is also known as the 'Mecca Stone' because Muhammad used an engraved Carnelian silver ring as a seal. Napoleon allegedly found a large octagonal Carnelian engraved with "the slave Abraham relying upon the merciful" from a battlefield during his Egyptian campaign.
One of the most prized Chalcedonies, Chrysoprase is named from the Greek 'chrysos' (gold) and 'prason' (leek), in reference to its green colour. Chrysoprase's green varies due to the hydrated silicates and nickel oxides present.
Jasper is Chalcedony's spotted, blotched and veined variety, named from the Latin 'iaspis', which means 'spotted stone'. Coming in over 50 different colour and pattern varieties, Jasper is historically associated with a mind-boggling array of esoteric powers.
Named from the Greek 'onyx' (fingernail or claw), Onyx was mythologically created when Cupid trimmed the fingernails of a sleeping Venus. Onyx is typically perceived as a black gem, but as a variety of Agate, is actually banded with white. Finely textured, Onyx also comes in banded chocolate, green, reddish-brown and white. Sardonyx is a blend of Sard and White Onyx. Once more precious than gold or silver, Sardonyx was highly valued in Rome as a seal stone because it apparently doesn't stick to wax. Roman General Publius Cornelius Scipio was a big fan of Sardonyx and many legionnaires went into battle wearing Sardonyx engraved with Mars (the god of war) for courage.
The best known variety of cat's eye or chatoyant Quartz, Tiger's Eye has lustrous yellow and golden brown stripes. Named for its resemblance to the eye of a tiger, Tiger's Eye is actually a macrocrystalline Quartz (large crystal), but is included here because of its appearance. Varieties include Bull's Eye (reddish-brown) and Hawk's Eye (bluish-green). The quintessential 'masculine' gem, it is a perennial favourite for signet rings and cufflinks.