·noun A cryptocrystalline, translucent variety of quartz, having usually a whitish color, and a luster nearly like wax.
Mentioned only in Rev. 21:19, as one of the precious stones in the foundation of the New Jerusalem. ...
Easton's Bible Dictionary
only in (Revelation 21:19) The name is applied in modern mineralogy to one of the varieties of agate...
William Smith's Bible Dictionary