Chalcedony (/kælˈsɛdəni/kal-SED-ə-nee, or /ˈkælsəˌdoʊni/KAL-sə-doh-nee)[2] is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite.[3] These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic. Chalcedony's standard chemical structure (based on the chemical structure of quartz) is SiO2 (silicon dioxide).
Chalcedony has a waxy luster, and may be semitransparent or translucent. 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. The color of chalcedony sold commercially is often enhanced by dyeing or heating.[4]
The name chalcedony comes from the Latin chalcedonius (alternatively spelled calchedonius) and is probably derived from the town of Chalcedon in Turkey.[5] The name appears in Pliny the Elder's Naturalis Historia as a term for a translucent kind of jaspis.[6] 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.[7] The term plasma is sometimes used to refer to green translucent chalcedony.[8]
A rare pseudomorph of a spiral Turritella-like snail shell that has been replaced by chalcedony
^Duda, Rudolf; Rejl, Lubos (1990). Minerals of the World. Arch Cape Press.
^Heaney, Peter J. (1994). "Structure and Chemistry of the low-pressure silica polymorphs". In Heaney, P. J.; Prewitt, C. T.; Gibbs, G. V. (eds.). Silica: Physical Behavior, geochemistry and materials applications. Reviews in Mineralogy. Vol. 29. pp. 1–40.
^Cite error: The named reference gemsociety was invoked but never defined (see the help page).
^Zwierlein-Diehl, Erika (2007). Antike Gemmen und ihr Nachleben. Berlin: Verlag Walter de Gruyter. S. 307. According to the OED, however, a connection with the town of Chalcedon is "very doubtful":Harper, Douglas. "Chalcedony". Online Etymology Dictionary.
^Pliny the Elder. "chapter 7". Naturalis Historiae. Vol. Book 37. p. 115.
^James Orr, ed. (1915). "Chalkēdōn". The International Standard Bible Encyclopaedia. The Howard-Severance company. p. 2859.
^Hart, Gilbert (1 Nov 1927). "The nomenclature of silica" (PDF). American Mineralogist. 12 (11). Mineralogical Society of America: 392.
Chalcedony (/kælˈsɛdəni/ kal-SED-ə-nee, or /ˈkælsəˌdoʊni/ KAL-sə-doh-nee) is a cryptocrystalline form of silica, composed of very fine intergrowths of...
Chrome chalcedony is a green variety of the mineral chalcedony, colored by small quantities of chromium. Its name is derived from Mutorashanga, a small...
Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases, is an opaque, impure variety of silica, usually...
the parallel-banded variety of chalcedony, a silicate mineral. Agate and onyx are both varieties of layered chalcedony that differ only in the form of...
Agate (/ˈæɡɪt/ AG-it) is the banded variety of chalcedony, which comes in a wide variety of colors. Agates are primarily formed within volcanic and metamorphic...
context of rings usually refers to a ring set with a chalcedony stone. Well-known types of chalcedony are carnelian, agate, and onyx. It is considered a...
interchangeably. Both carnelian and sard are varieties of the silica mineral chalcedony colored by impurities of iron oxide. The color can vary greatly, ranging...
valid species: Adamantine spar (variety of corundum) Agate (variety of chalcedony and quartz) Alabaster (variety of gypsum) Alexandrite (variety of chrysoberyl)...
while others have purple amethyst crystals. Still others can have agate, chalcedony, or jasper banding or crystals such as calcite, dolomite, celestite, etc...
Chrysoprase, chrysophrase or chrysoprasus is a gemstone variety of chalcedony (a cryptocrystalline form of silica) that contains small quantities of nickel...
chrysocolla may be a mixture of the copper hydroxide spertiniite and chalcedony. The name chrysocolla comes from the Ancient Greek χρυσός (khrusós) and...
Fire agate, a variety of chalcedony, is a semi-precious natural gemstone discovered so far only in certain areas of central and northern Mexico and the...
Pietersite is a commercial term for a variety of the mineral chalcedony. Originating from Namibia and China, where it is mined for use as a decorative...
Enhydros are closely related to fluid inclusions, but are composed of chalcedony. The formation of enhydros is still an ongoing process, with specimens...
opaque, while the transparent varieties tend to be macrocrystalline. Chalcedony is a cryptocrystalline form of silica consisting of fine intergrowths...
to over a meter (three feet) across. They usually contain centres of chalcedony which may have been fractured followed by deposition of agate, jasper...
which they named chrysoprase from its similarity to that green form of chalcedony. Fluorescent uranium Depression glass A uranium glass cakeplate glowing...
a semi-precious gemstone formed from silicon dioxide. It is a form of chalcedony which includes minerals of a green color embedded in the stone, forming...
use by the Navy on December 15, 1941 and being commissioned as the USS Chalcedony designated PYC-16 on weather duty for the Hawaiian Sea Frontier. In 1947...
Elaphria chalcedonia, the chalcedony midget moth, is a moth of the family Noctuidae. It is found in North America, where it has been recorded from the...
Pliny, "Hist. nat.", XXXVII, liv). The stone belongs to the silex family (chalcedony species) and is formed by deposits of siliceous beds in hollows of rocks...
have been replicated with minerals (mostly silica in the form of opal, chalcedony, or quartz). In some instances, the original structure of the stem tissue...
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