Sardonyx

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A precious stone associated with one of the foundations of the holy Jerusalem (Rev. 21:20). The word does not occur in the AV of the Old Testament. Aquila, in his Greek version, uses it for the onyx in Genesis 2:12. It is judged to be a variety of chalcedony, or of agate, of various colors, with stripes of a different shade.
Chalcedony Var. Agate