Watson's Biblical & Theological Dictionary
שהם , Genesis 2:12; Exodus 25:7; Exodus 28:9; Exodus 28:20; Exodus 35:27; Exodus 39:6; 1 Chronicles 29:2; Job 28:16; Ezekiel 28:13 . A precious stone, so called from the Greek ονυξ , the nail, to the colour of which it nearly approaches. It is first mentioned with the gold and bdellium of the river Pison in Eden: but the meaning of the Hebrew word is not easily determined. The Septuagint render it, in different places, the sardius, beryl, sapphire, emerald, &c. Such names are often ambiguous, even in Greek and Latin, and no wonder if they are more so in Hebrew. In Exodus 28:9-10 , a direction is given that two onyx stones should be fastened on the ephod of the high priest, on which were to be graven the names of the children of Israel, like the engravings on a signet; six of the names on one stone, and six on the other. In 1 Chronicles 29:2 , onyx stones are among the things prepared by David for the temple. The author of "Scripture Illustrated" observes, upon this passage, that "the word onyx is equivocal; signifying, first, a precious stone or gem; and secondly, a marble called in Greek onychites, which Pliny mentions as a stone of Caramania.
Antiquity gave both these stones this name, because of their resemblance to the nail of the fingers. The onyx of the high priest's pectoral was, no doubt, the gem onyx; the stone prepared by David was the marble onyx, or rather onychus; for one would hardly think that gems of any kind were used externally in such a building, but variegated marble may readily be admitted."
These files are public domain.
Text Courtesy of BibleSupport.com. Used by Permission.
Watson, Richard. Entry for 'Onyx'. Richard Watson's Biblical & Theological Dictionary. https://www.studylight.org/dictionaries/eng/wtd/o/onyx.html. 1831-2.