King James Bible Dictionary

Heb. pitdah (Ezekiel 28:13; Revelation 21:20), a golden yellow or "green" stone brought from Cush or Ethiopia (Job 28:19). It was the second stone in the first row in the breastplate of the high priest, and had the name of Simeon inscribed on it (Exodus 28:17). It is probably the chrysolite of the moderns.

A precious stone
Ezekiel 28:13; Revelation 21:20

In the breastplate
Exodus 28:17; Exodus 39:10

Ethiopian, celebrated
Job 28:19

one of the gems used in the high priest's breastplate, (Exodus 28:17; 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.

TO'PAZ, noun [Gr.] A mineral, said to be so called from Topazos, a small isle in the Arabic gulf, where the Romans obtained a stone which they called by this name, but which is the chrysolite of the moderns. The topaz is of a yellowish color. It sometimes occurs in masses, but more generally crystallized in rectangular octahedrons. topaz is valued as a gem or precious stone, and is used in jewelry. It consists of silex, fluoric acid and alumin, in the following proportions; alumin 57 parts, silex 34, and fluoric acid 7 or 8.

Of topaz there are three subspecies, common topaz shorlite and physalite.

TOPAZ'OLITE, noun A variety of precious garnet, of a topaz yellow color, or an olive green.