Crystal
Easton's Dictionary
(Ezek. 1:22, with the epithet “terrible,” as dazzling the spectators with its brightness). The word occurs in Rev. 4:6; 21:11; 22:1. It is a stone of the flint order, the most refined kind of quartz. The Greek word here used means also literally “ice.” The ancients regarded the crystal as only pure water congealed into extreme hardness by great length of time.
Smith's Dictionary
the representative in the Authorized Version of two Hebrew words.
Zecucith occurs only in (Job 28:17) where “glass” probably is intended. kerach occurs in numerous passages in the Old Testament to denote “ice,” “frost,” etc.; but once only (Ezekiel 1:22) as is generally understood, to signify “crystal.” The ancients supposed rock-crystal to be merely ice congealed by intense cold. The similarity of appearance between ice and crystal caused no doubt the identity of the terms to express these substances. The Greek word occurs in (Revelation 4:6; 21:1) It may mean either “ice” or “crystal.”