Adam Clarke on Genesis 2:12

There is bdellium (בדלח bedolach) and the onyx stone, אבן השהם eben hashshoham - Bochart thinks that the bedolach or bdellium means the pearl-oyster; and shoham is generally understood to mean the onyx, or species of agate, a precious stone which has its name from ονυξ a man's nail, to the color of which it nearly approaches. It is impossible to say what is the precise meaning of the original words; and at this distance of time and place it is of little consequence.