Onyx

"A hail; claw; hoof, (Heb. shoham), a precious stone adorning the" breast-plate of the high priest and the shoulders of the ephod "(Ex. 28:9-12, 20; 35:27; Job 28:16; Ezek. 28:13). It was found" in the land of Havilah (Gen. 2:12). The LXX. translates the "Hebrew word by smaragdos, an emerald. Some think that the" sardonyx is meant. But the onyx differs from the sardonyx in "this, that while the latter has two layers (black and white) the" "former has three (black, white, and red)."