THE GOLD OF THAT LAND: Biblical Minerals & Rocks  


53.     ruby 

Hebrew: pnyn. Job 28:18; Proverbs 3:15, 8:11, 20:15, 31:10; Lamentations 4:7.

Probable Identification:

    Biblical ruby is a red garnet or red coral. See "CARBUNCLE."

    Rubies and sapphires were unknown in ancient Egypt and Mesopotamia. Numerous examples of historic royal jewels that were formerly called rubies or "Balas rubies" are actually spinel. A 400 karat red spinel, for instance, ornaments the Russian imperial crown. Siberian ruby is rubellite, a pink-to-red variety of corundum. A famous large specimen adorns the crown of St. Wenceslas, made in 1347 for Charles IV of Bohemia.


    Ruby is the red gem variety of crystalline corundum (Al2O3, alumina), the second hardest mineral next to diamond. Corundum crystals have a prismatic habit, hexagonal-rhombohedral form, vitreous to adamantine luster, and vary from opaque to translucent to transparent. In color, they may be white, gray, green, golden, orange, red, purple, brown, blue or black. Emery is black corundum. Ruby is gem corundum with a deep red color imparted by minute traces of chromium, while sapphire is blue or black. Large, fine rubies are rarer than sapphires of the same size and quality and therefore more valuable. Gem-quality corundum in other colors is usually named after other gems with the prefix "oriental," despite the objections of jewelers. Oriental amethyst is therefore purple corundum, oriental emerald is green corundum, and oriental topaz is yellow corundum.

    Corundum occurs as an accessory mineral in metamorphic rocks and a few silica-poor igneous rocks. Associated minerals include chlorite, micas, olivine, serpentine, magnetite, spinel, diaspore, and kyanite. The most famous source of both rubies and sapphires is the Mogok Stone Tract, a district of 400 square miles lying 90 km north of Mandalay in Burma. These rubies of the classic deep red color occur in the weathered gravelly solution residue of a metamorphosed limestone. Rubies outnumber blue sapphires near Mogok by about 500 to 1, but sapphires are more common near Kathe. Tourmaline, spinel, and other resistant stones also abound in the gravels. Afghanistan, Ceylon, the modern Sri Lanka, Cambodia and Thailand also supplied rubies and sapphires until the introduction of the Linde process made possible the synthesis of artificial rubies and sapphires indistinguishable in quality from natural stones. Adding a trace of titanium produces star rubies and star sapphires in which tiny oriented needles of rutile produce the star effect.

    Corundum or alumina has an electrical storage capacity three times greater than silicon dioxide, and alumina films have prospects for application in the next generation of transistors, "on/off" switching devices for semiconducting circuits. They could make computer circuits smaller, faster, and more reliable.

Scripturally, wisdom (Job 28:18) and virtuous women  (Proverbs 31) are worth far more than rubies, the most precious of gemstones.


   Hurlbut, 1952, op. cit.; 228.

   Ralph, Jolyon, 1993-2004.

Schumann, op. cit.; 82-85.

Webster, op. cit.; 63-69.

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Last updated: 05/13/06.