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Fausset's Bible Dictionary [1]

Leshem Hebrew, the first in the third row of jewels on the high priest's breast-plate ( Exodus 28:19). Septuagint and Vulgate translated ligure, and as Theophrastus (de Lap. 29) and Pliny (H. N. 37:11) say amber came from Liguria, probably Septuagint and Vulgate understand by "ligure" amber. But Theophrastus distinguishes the lyncurium of Liguria from electron, "amber." Amber is too soft for engraving; but lyncurium was hard, and at the same time attracted light particles of wood, iron and brass. The red variety of tourmaline, the rubellite, which is electrically polar when heated, maybe meant. The jacinth also is electric.

Smith's Bible Dictionary [2]

Ligure. (Hebrew, leshem ). A precious stone mentioned in  Exodus 28:19;  Exodus 39:12 as the first in the third row of the high priest's breastplate. It is impossible to say, with any certainty, what stone is denoted by the Hebrew term; but perhaps Tourmaline , or more definitely the red variety known as Rubellite , has better claims than any other mineral. Rubellite is a hard stone, and used as a gem, and is sometimes sold for Red Sapphire .

People's Dictionary of the Bible [3]

Ligure, Heb. Leshem . A precious stone mentioned in  Exodus 28:19;  Exodus 39:12, R. V. "Jacinth," as the first in the third row of the high priest's breastplate. Perhaps tourmaline, or more definitely the red variety known as rubellite, is the stone meant. Rubellite is a hard stone, and used as a gem, and is sometimes sold for red sapphire.

Morrish Bible Dictionary [4]

leshem. The first in the third row of gems in the breastplate. It is supposed by some to be the hyacinth, by others the lyncurium , and by others amber; but its identification is uncertain.  Exodus 28:19;  Exodus 39:12 .

Watson's Biblical & Theological Dictionary [5]

לשם ,  Exodus 28:19;  Exodus 39:12 , a precious stone of a deep red colour, with a considerable tinge of yellow. Theophrastus and Pliny describe it as resembling the carbuncle, of a brightness sparkling like fire.

American Tract Society Bible Dictionary [6]

Probably the same with the jacinth, a stone in the high priest's breastplate,  Exodus 28:19;  39:12 , said to have been of a deep and brilliant red color, with a tinge of yellow, and transparent.

Holman Bible Dictionary [7]

 Exodus 28:19Minerals And Metals

Easton's Bible Dictionary [8]

 Exodus 28:19,39:12

Hastings' Dictionary of the Bible [9]

Ligure See Jewels and Precious Stones.

King James Dictionary [10]

LIG'URE, n. A kind of precious stone.

Webster's Dictionary [11]

(n.) A kind of precious stone.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [12]

( לֶשֶׁם , Le'Shenm, supposed to be from an old root preserved in the Arab., and signifying To Taste) Oc curs but twice ( Exodus 28:19;  Exodus 39:12) as the name of the first stone in the third row on the high-priest's breastplate, where the Sept. renders Λιγύριον (apparently alluding to the above derivation), and is followed by the Vulg. Ligyurius, as well as the A.V. So also Josephus (War, 5:5,7). " The word Ligulre is unknown in modern mineralogy. Phillips (Mineraslogy, page 87) mentions Ligurite, the fragments of which are uneven and transparent, with a vitreous luster. It occurs in a sort of talcose rock in the banks of a river in the Apennines" (Smith). The classical ligure (or Λυγκούριον ) was thought to be a species of amber (see Moore, Anc. Min. page 106), although ancient authors speak uncertainly respecting it (Pliny, Hist. Nat. 37:11, 13; Theophrastus, De Lalpid. c. 50), and assign a false derivation to the name (see Gesenius, Thesaur. Heb. page 763). The Hebrew word has been thought to designate the same stone as the Jacinth (Braunius, De Vestitu Sacerd. 2:14), although others adhere to the Opal as corresponding better with the ancient figure (Rosenm Ü ller, Sch. In Lexod. 28:19). "Dr. Woodward and some old commentators have supposed that it was some kind of Belemnite, because, as these fossils contain bituminous particles, they have thought that they have been able to detect, upon heating or rubbing pieces of them the absurd origin which Theophrastus (Frag. 2:28, 31; 15:2, edit. Schneider) and Pliny (H.N. 37:3) ascribe to the lyncyrium. As to the belief that amber is denoted by this word, Theophrastus, in the passage cited above, has given a detailed description of the stone, and clearly distinguishes it from electron, or amber. Amber, moreover, is too soft for engraving upon, while the lynncyrium was a hard stone, out of which seals were made." (See Gem).

Beckmann (Hist. Invent. 1:87, Bohn) believes, with Braun, Epiphanius, and J. de Laet, that the description of the Lyncyrium agrees well with the hyacinth-stone of modern mineralogists, especially that species which is described as being of an orange-yellow color, passing on into a reddish-brown (see Rosenm Ü ller, Bibl. Alterth. IV, 1:28). The hyacinth is a variety of crystallized zircon, containing also iron, which usually gives it a reddish or brown color. It generally occurs in four-sided prisms, terminated by four rhombic planes. It is diaphanous, glossy, and hard. It occurs in the beds of rivers, the best being brought from the West Indies, but is now little esteemed as a gem, although the ancients used it for engraving. "With this supposition (that the lyncyrium is identical with the jacinth or hyacinth) Hill (Notes on Theophrastus on Stones, § 50, page 166) and Rosenm Ü ller (Mineral. of Bible, page 36; Bib. Cab.) agree. It must be confessed, however, that this opinion is far from satisfactory; for Theophrastus, speaking of the properties of the lyncyrium, says that it attracts not only light particles of wood, but fragments of iron and brass. Now there is no peculiar attractive power in the hyacinth; nor is Beckmann's explanation of this point sufficient.

He says: 'If we consider its (the lyncyrium's) attracting of small bodies in the same light which our hyacinth has in common with all stones of the glassy species. I cannot see anything to controvert this opinion, and to induce us to believe the lyncyrium and the tourmaline to be the same.' But surely the lyncyrium, whatever it be, had in a marked manner magnetic properties; indeed, the term was applied to the stone on this very account, for the Greek name ligurion appears to be derived from Λείχειν , 'to lick,' 'to attract,' and doubtless was selected by the Sept. for this reason to express the Hebrew word, which has a similar derivation. Hence Dr. Watson (Philos. Tirans. 51:394) identifies the Greek hyncyrium with the tournmaline, or, more definitely, with the red variety known as rubellite, which is a hard stone, and used as a gem, and sometimes sold for red sapphire. Tourmaline becomes, as is well known, electrically polar when heated. Beckmann's objection, that had Theophrastus been acquainted with the tourmaline, he would have remarked that it did not acquire its attractive power till it was heated,' is answered by his own admission on the passage, quoted from the Hist. de l'Academie for 1717, page 7 (see Bechmann, 1:91). Tourmaline is a mineral found in many parts of the world. The duke de Noya purchased two of these stones in Holland, which are there called aschentrikker. Linnaus, in his preface to the Flora Zeylandica, mentions the stone under the name of lapis electricus from Ceylon. The natives call it tournamal (Philippians Trans. 1.c.). Many of the precious stones which were in the possession of the Israelites during their wanderings were no doubt obtained from the Egyptians, who might have procured from the Tyrian merchants specimens from even India and Ceylon, etc. The fine specimen of rubellite now in the British Museum belonged formerly to the king of Ava."

Kitto's Popular Cyclopedia of Biblial Literature [13]

The Hebrew word Leshem is thus rendered in;; and in it is put as equivalent to the Jacinth or Hyacinth; and it is certain that the ligure and the jacinth are regarded as the same stone. The prevailing color of the jacinth is orange-yellow-red; which passes over sometimes into reddish-brown, sometimes into brownish and pale red, and sometimes into imperfect pistachio green. It is harder than the emerald, but the artists of antiquity frequently engraved upon it. It comes to us from the East Indies.

International Standard Bible Encyclopedia [14]

lig´ū́r (  Exodus 28:19;  Exodus 39:12 the King James Version, the Revised Version (British and American) "jacinth"). See Stones , Precious .