chalcedony

Borrowed from Latin chalcedonius, probably derived from the name of the town Chalcedon in Asia Minor.

• IPA^(key): /kælˈsɛdəni/

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A cut and polished chalcedony geode.

chalcedony (countable and uncountable, plural chalcedonies)

1. A form of fine-grained quartz that is nearly transparent or has a milky translucence; it fractures conchoidally.
   • 2012 March 1, Lee A. Groat, “Gemstones”, in American Scientist‎, volume 100, number 2, page 128:

     Although there are dozens of different types of gems, among the best known and most important are […] . (Common gem materials not addressed in this article include amber, amethyst, chalcedony, garnet, lazurite, malachite, opals, peridot, rhodonite, spinel, tourmaline, turquoise and zircon.)

• (noun: types of minerals) agate, chert, flint, moganite
• (adjective) conchoidal
• (adverb) conchoidally
• (noun) break, fracture, flake, shatter
• (verb) knapp, break, fracture, flake, shatter

• “Chalcedony” in David Barthelmy, Webmineral Mineralogy Database, 1997–.
• “chalcedony”, in Mindat.org‎, Hudson Institute of Mineralogy, accessed 29 August 2016.