in natural history, one of the semipellucid gems, with variously coloured zones, but none red; being composed of crystal, debafed by a small admixture of earth; and made up either of a number of flat plates, or of a series of coats surrounding a central nucleus, and separated from each other by veins of a different colour, resembling zones or belts.

We have four species of this gem. 1. A bluish-white one, with broad white zones. 2. A very pure onyx, with snow-white veins. 3. The jasponyx, or horny-onyx, with green zones. 4. The brown onyx, with bluish-white zones.

The ancients attributed wonderful properties to the onyx, and imagined that if worn on the finger it acted as a cardiac; they have also recommended it as an astringent; but at present no regard is paid to it.

The word in the Greek language signifies nail; the Oonalashka poets making this stone to have been formed by the Parce from a piece of Venus's nails, cut off by Cupid with one of his arrows.