![]() In the 19th century, Idar-Oberstein, Germany, became the world's largest chalcedony processing center, working mostly on agates. (Jewish tradition states that Moses' brother Aaron wore the Breastplate, with inscribed gems representing the twelve tribes of Israel.) The Breastplate supposedly included jasper, chrysoprase and sardonyx, and there is some debate as to whether other agates were also used. The term chalcedony is derived from the name of the ancient Greek town Chalkedon in Asia Minor, in modern English usually spelled Chalcedon, today the Kadıköy district of Istanbul.Īccording to tradition, at least three varieties of chalcedony were used in the Jewish High Priest's Breastplate. Hot wax would not stick to it so it was often used to make seal impressions. People living along the Central Asian trade routes used various forms of chalcedony, including carnelian, to carve intaglios, ring bezels (the upper faceted portion of a gem projecting from the ring setting), and beads that show strong Greco-Roman influence.įine examples of first century objects made from chalcedony, possibly Kushan, were found in recent years at Tillya-tepe in north-western Afghanistan. In the Bronze Age chalcedony was in use in the Mediterranean region for example, on Minoan Crete at the Palace of Knossos, chalcedony seals have been recovered dating to circa 1800 BC. Pre-contact uses described in the twentieth century included ceremonial stone knives. History Chalcedony cameo of Titus head, 2nd Century ADĬhalcedony was used in tool making as early as 32,000 BP in Central Australia where archaeological studies at sites in the Cleland Hills uncovered flakes from stone brought in from quarries many kilometres away. Landscape agate is chalcedony with a number of different mineral impurities making the stone resemble landscapes. Fire agate shows iridescent phenomena on a brown background iris agate shows exceptional iridescence when light (especially pinpointed light) is shone through the stone. Opaque varieties are sometimes referred to as jasper. The more notable varieties of chalcedony are as follows:Īgate is a variety of chalcedony characterized by either transparency or color patterns, such as multi-colored curved or angular banding. Many semi-precious gemstones are in fact forms of chalcedony. ![]() ![]() A rare Moroccan pseudomorph of a spiral Turritella-like snail shell that has been replaced by chalcedony Varieties Ĭhalcedony occurs in a wide range of varieties. ![]() The term plasma is sometimes used to refer to green translucent chalcedony. Another reference to a gem by the name of khalkedón ( χαλκηδών) is found in the Book of Revelation (21:19) however, it is a hapax legomenon found nowhere else in the Bible, so it is hard to tell whether the precious gem mentioned in Revelation is the same as the mineral known by this name today. The name appears in Pliny the Elder's Naturalis Historia as a term for a translucent kind of jaspis. The name chalcedony comes from the Latin chalcedonius (alternatively spelled calchedonius) and is probably derived from the town of Chalcedon in Turkey. The color of chalcedony sold commercially is often enhanced by dyeing or heating. It can assume a wide range of colors, but those most commonly seen are white to gray, grayish-blue or a shade of brown ranging from pale to nearly black. Chalcedony's standard chemical structure (based on the chemical structure of quartz) is SiO 2 ( silicon dioxide).Ĭhalcedony has a waxy luster, and may be semitransparent or translucent. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic. Gettens, G.L.Microcrystalline varieties of silica, may contain moganite as well ChalcedonyĬhalcedony ( / k æ l ˈ s ɛ d ə n i/ kal- SED-ə-nee, or / ˈ k æ l s ə ˌ d oʊ n i/ KAL-sə-doh-nee) is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. ![]() Hvid (Dan.) Weiss (Deut.) Weiß (Deut.) blanco (Esp.) blanc (Fr.) bianco (It.) albus (Lat.) wit (Ned.) branco (Port.) vit (Sven.)Ĭharacteristics of Common White Pigments Resources and Citations
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