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Watson's Biblical & Theological Dictionary [1]

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."

Fausset's Bible Dictionary [2]

Shoham . Found in the land of Havilah ( Genesis 2:12). Onyx means "nail"; then the agate, resembling in color a man's nail. Two onyx stones, with six names of Israel's tribes engraven on each, were on the high priest's shoulders as "stones of memorial unto Israel" ( Exodus 28:9-12). The onyx was the second stone in the fourth row on his breast-plate ( Exodus 28:20). Josephus (Ant. 3:7, section 5) calls the shoulder stones "sardonyxes" (Compounded Of Sard Or Chalcedony And Onyx, Deep Red And Milkwhite Layers Alternating) .

David's onyxes "prepared for the house of his God" ( 1 Chronicles 29:2) probably came from Tyre ( Ezekiel 28:13). Tyre's king, like the high priest with his precious stones, was the type of humanity in its unfallen perfection in Eden; antichrist will usurp the divine King Priest's office ( Zechariah 6:13; compare  Acts 12:21-23). Job ( Job 28:16) calls it "precious," but not so much so as "wisdom," priceless in worth. The Arabian sardonyxes have a black ground color, Sachma , is Arabic "blackness"; opaque white covers black or blue strata. Sahara in Arabic means "to be pale"; from whence Gesenius derives Shoham . The kinds of onyx and sardonyx vary so as to answer to either derivation. The onyx has two strata, the sardonyx has three.

Smith's Bible Dictionary [3]

Onyx. (A Nail). Onyx is the translation of the Hebrew shoham ; but there is some doubt as to its signification. Some writers believe that the "Beryl" is intended; but the balance of authority, is in favor of some variety of the Onyx .

("The onyx is not a transparent stone, but as the color of the flesh appears through the nail, (Greek, onyx ), on the human body, so the reddish mass which is below, shines delicately through the whitish surface of the onyx. There are several varieties. White and reddish stripes alternating form the Sardonyx ; white and reddish gray, the Chalcedony . When polished, it has a fine lustre, and is easily wrought into a gem of great beauty." - Rosenmiller.

American Tract Society Bible Dictionary [4]

A nail, the eleventh stone in the high priest's breastplate,  Exodus 28:20 . The modern onyx has some resemblance to the agate; and the color of the body of the stone is like that of the human nail; hence its name. The Hebrew word so translated is not known with certainty to signify the onyx; but denoted some valuable stone,  Genesis 2:12;  Exodus 25:7;  28:9-12,20 . A species of marble resembling the onyx was known to the Greeks, and may have been the "onyx-stones" stored up by David for the temple,  1 Chronicles 29:2 .

People's Dictionary of the Bible [5]

Onyx.  Genesis 2:12;  Exodus 28:9;  Exodus 28:20;  Exodus 35:9;  Exodus 35:27;  1 Chronicles 29:2;  Job 28:16;  Ezekiel 28:13. Opinions differ as to the gem intended by this word; some prefer translating it "beryl." The onyx has its particles arranged in parallel layers; white alternating with blue, gray, or brown. It was much used by the ancients for cameos.

Morrish Bible Dictionary [6]

The precious stone in each shoulder piece of the ephod, and one of those in the breastplate of the high priest. Its Hebrew name is shoham; but this has five different translations in the LXX, and its identity is uncertain.   Genesis 2:12;  Exodus 25:7;  Exodus 28:9,20;  Exodus 35:9,27;  Exodus 39:6,13;  1 Chronicles 29:2;  Job 28:16   Ezekiel 28:13 .

Easton's Bible Dictionary [7]

 Exodus 28:9-12,20 35:27 Job 28:16 Ezekiel 28:13 Genesis 2:12

Hawker's Poor Man's Concordance And Dictionary [8]

A precious stone: it formed a part in the high priest's breastplate. ( Exodus 28:20)

Webster's Dictionary [9]

(n.) Chalcedony in parallel layers of different shades of color. It is used for making cameos, the figure being cut in one layer with the next as a ground.

King James Dictionary [10]

ON'YX, n. Gr. a nail. L. onyx. A semi-pellucid gem with variously colored zones or veins, a variety of chalcedony.

Holman Bible Dictionary [11]

Minerals And Metals

Hastings' Dictionary of the Bible [12]

ONYX. See Jewels and Precious Stones, Onycha.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [13]

the uniform translation in the English version of the Hebrew word shoharn, שֹׁהִם , which occurs in eleven passages of the O.T. The renderings of the old interpreters are various, and often inconsistent with each other. The Sept. in  Exodus 25:7;  Exodus 35:9, renders Σάρδιος , Sardius; in  Exodus 28:9;  Exodus 39:6, Σμάραγδος , smaragdus; in  Ezekiel 28:13, Σάπφειρος , Sapphire; elsewhere Onyx or Beryl. This strange inconsistency could spring only from ignorance and conjecture. Yet the Venetian MS. has always Κρύσταλλος , crystal. The Sept. in Job ( Job 28:16), with Symmachius ( Genesis 2:12;  Exodus 25:7), Josephus ( Ant. 3:7, 6), and Jerome, (usually) understand the gem which was called by the Greeks Ὄνυξ ; onyx, from its resemblance in color to a human nail. This seems to be favored by comparing the similar Arabic root Saham, denoting Paleness (see Pliny, Hist. Nat. 37:6, 24; Edrisi, 1:150, ed. Jaubert). The Shechem stone is mentioned ( Genesis 2:12) as a product of the land of Havilah. Two of these stones, upon which were engraven the names of the children of Israel, six on either stone, adorned the shoulders of the high-priest's ephod ( Exodus 28:9-12), and were to be worn as "stones of memorial" (see Kalisch on Exodus L.C. ) . Ashdham was also the second stone in the fourth row of the sacerdotal breastplate ( Exodus 28:20). Shohain stones were collected by David for adorning the Temple ( 1 Chronicles 29:2). In  Job 28:16, it is said that wisdom "cannot be valued with the gold of Ophir, with the precious Shdham Or the sapphire." The Shoham is mentioned as one of the treasures of the king of Tyre ( Ezekiel 28:13).

There is nothing in the contexts of the several passages where the Hebrew term occurs to help us to determine its signification. Braun ( De Vest. Sac. Heb. p. 727) has endeavored to show that the sardonyx is the stone indicated, and his remarks are well worthy of careful perusal. Josephus ( Ant. 3:7, 5, and War, v. 5, 7) expressly states that the shoulder-stones of the high-priest were formed of two large sardonyxes, an onyx being, in his description, the second stone in the fourth row of the breastplate. The sardonyx, however, is but that variety of the. onyx in which white and reddish stripes alternate. Rosenm Ü ller remarks ( Bibl. Alterth. 4:1): "The onyx is not a transparent stone; but as the color of the flesh appears through the nail (in Greek called Onyx ) on the human body, so the reddish mass which is below shines delicately through the whitish surface of the onyx. There are several varieties of this stone, according to the manner in which thin strata of different colors alternate in it; white and reddish stripes alternating, form the sardonyx; white and reddish-gray, the chalcedonlyx; grayish-white and yellow-brown, the memphitonyx. The onyx most esteemed by the ancients had milk-white and brown or white and black strata. When polished, it has a fine lustre; it is easily wrought into a gem of great beauty. The different kinds of onyx have, from. early antiquity, been used for rings, for seals and cameos, and, accordingly, they are frequently found in collections of antiques." Braun traces shodham to the Arabic sachma, "blackness:" "Of such a color," says he, "are the Arabian sardonyxes, which have a black ground-color." This agrees essentially with Mr. King's remarks (Antique Gems, p. 9): "The Arabian species," he says, "were formed of black or blue strata, covered by one of opaque white; over which again was a third of a vermilion color." As to the "onyx" of  Sirach 24:15, (See Onycha).

But the more usual interpretation of the Hebrew word shoham is beryl. This is the rendering given by the Syriac, the Targums of Onkelos and Jonathan, and the Sept. in two places ( Exodus 28:20;  Exodus 39:13); and it is supported by Bellermann ( Urnim, p. 64), Winer ( Real- Worterbuch, 1:283, 4th ed.), Rosenm Ü ller (ut sup.), and others. This is the same stone called by the Sept. ( Genesis 2:12) Λίθος Πράσινος , the Leek-Stone, i.e. the Stone Of A Leek-Green Color; Latin, Porraceus. (But Schleussner, s.v., makes this the Sardonyx. ) According to Pliny ( Hist. Nat. 37:5, 20), the beryl is found in India, and but rarely elsewhere, and is of the highest value when like the sea in color. (See Beryl). For other explanations, see Wahlius, Asien, p. 856; Benfev, Encyclop. Halens. II, 17:14; Gesenius, Thesaur. p. 1370. (See Gem).

Kitto's Popular Cyclopedia of Biblial Literature [14]

O´nyx. The Hebrew word translated by 'onyx-stone' in , is different from that so rendered in the descriptions of the breastplate of the high-priest , and it is doubtful if the onyx is really intended by either. This stone has a whitish ground, and is variegated with bands of white and brown which run parallel to each other. It is a semi-pellucid stone of a fine flinty texture, taking an excellent polish, and is strictly of the flint or siliceous class. 'Onyx' is the Greek word for the human nail; and the stone takes its name from the resemblance of the ground-color to that lunate spot at the base of the nail.

The Nuttall Encyclopedia [15]

A variety of agate or chalcedony, in which occur even layers of white and black or white and brown, sharply defined in good specimens; they come from India, and are highly valued for cameo-cutting.