Chalcedony

Chalcedony - (Easton's Bible Dictionary)

Mentioned only in Rev. 21:19, as one of the precious stones in the foundation of the New Jerusalem. The name of this stone is derived from Chalcedon, where it is said to have been first discovered. In modern mineralogy this is the name of an agate-like quartz of a bluish colour. Pliny so names the Indian ruby. The mineral intended in Revelation is probably the Hebrew nophekh, translated "emerald" (Ex. 28:18; 39:11; Ezek. 27:16; 28:13). It is rendered "anthrax" in the LXX., and "carbunculus" in the Vulgate. (See [109]CARBUNCLE.)

Chalcedony - (Webster's 1828 Dictionary)

CHALCEDONY, n. A subspecies of quartz, a mineral called also white agate, resembling milk diluted with water, and more or less clouded or opake, with veins, circles and spots. It is used in jewelry.

The varieties of chalcedony are common chalcedony, heliotrope, chrysoprase, plasma, onyx, sard and sardonyx.