Two onyx stones. The correctness of this rendering has been much disputed. The LXX. give σμάραγδος, "emeraid." as the Greek equivalent in the present passage, while many argue for the beryl (Winer, Rosenmuller, Bollermann), and others for the sardonyx.
This last rendering has the support of Josephus and Aquila. The sardonyx is, in fact, nothing but the best kind of onyx, differing from the onyx by having three layers—black, white, and red—instead of two—black and white—only.
When large, it fetches a high price, as much as a thousand pounds having been asked for one by a dealer recently. The probability is, that it is the stone here intended. It is an excellent material for engraving.
With respect to the possibility of Moses having in the congregation persons who could engrave the sardonyx, we may remark that the Egyptians cut stones quite as hard, from a date long anterior to the exodus.
Grave on them the names of the children of Israel. Egyptian names are frequently found engraved on rings and amulets in hard stone; these rings and amulets date from the time of the twelfth dynasty. The names here intended are evidently the Israelite tribe names, which are reckoned as twelve, the double tribe of Joseph counting as one only.
(Compare Numbers 1:10; Deuteronomy 33:13-17.