Definition from Wiktionary, the free dictionary
chalcedony (plural chalcedonies)
- 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”, 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.)
form of fine-grained quartz