Smith's Bible Dictionary

Topaz one of the gems used in the high priest’s breastplate, (Exodus 28:17; Exodus 39:10; Ezekiel 28:13) one of the foundations also of the New Jerusalem, in St. John’s description of the city. (Revelation 21:20) The topaz of the ancient Greeks and Romans is generally allowed to be our chrysolite, while their chrysolite is our topaz. Chrysolite is a silicate of magnesia and iron; it is so son as to lose its polish unless carefully used. It varies in color from a pale-green to a bottle-green. It is supposed that its name was derived from Topazos, an island in the Red Sea where these stones were procured.