THE GOLD OF THAT LAND: Biblical Minerals & Rocks  


 

 10.     beryl

Hebrew: tarshîsh, or gem of Tarshish (Spain). Exodus 28:20, 39:13; Song of Solomon 5:14; Ezekiel 1:16, 10:9, 28:13; Daniel 10:6.

Greek: berullos. Revelation 21:20.

Probable Identification: tarshish is yellow CITRINE quartz while berullos is MALACHITE.

    The traditional identification of tarshîsh with beryl comes from the Targum without support from the Septuagint. Furthermore, beryl does not occur in Spain, but citrine, a yellow variety of crystalline quartz does.

Mineralogy:

    Citrine is among the less common, most valued gem varieties of quartz. A trace of iron imparts its lemon-yellow tint, which can be counterfeited by heat treatment of amethyst or rose quartz. Like amethyst, citrine occurs in geodes, and specimens from Campo Belo and Sete Lagoas in the Brazilian state of Minas Gerais are improperly known as "Brazilian topaz." Other sources are Argentina, Burma, India, Namibia, Russia, Scotland and Spain. Citrines make attractive pendants, ring stones, and necklaces.

    Beryl is beryllium aluminum silicate (Be3Al2Si6O18), which forms prismatic hexagonal crystals in pegmatite dikes in granite. It has a hardness of 7.5 to 8 and an average specific gravity of 2.7. Clear crystals are harder than cloudy ones. Fresh surfaces have a higher, more greasy luster than quartz. Beryls are more brittle than quartz because they fracture parallel to prism faces but cleave at a 90o angle to the fracture direction. Natural fractures in a crystal are visible as flaws or internal cracks.

    The Greeks lumped all colors of beryl together as berullos, while the Egyptians called all greenish stones mafek. Beryls range from white to pink and red, yellow to brown, and green to blue, in all intensities. Colored beryls vary in hue and intensity when observed from different directions because their optical properties are not uniform in all directions. Although most beryls are uniformly colored, striking examples of zoning occur in specimens from Brazil, North Carolina, Siberia, and South Africa. Zoning patterns reflect changing chemistry during crystal growth. In the most common zoning pattern, darker zones envelope a colorless core like growth rings in a tree trunk.

    Deep green emerald with a hint of blue is considered the most precious gem variety of beryl today, and its rarity makes fine emeralds more valuable than diamond. Emerald owes its green color to a trace of chromium or vanadium, while iron adds a blue tint. The association of pyrite with emerald, however, minimizes the blueness to the nominal level that accounts for the classic green hue of  Colombian emeralds. Goshenite is clear, colorless beryl without impurities. A trace of ferric iron imparts tints to aquamarine ranging from pale blue-green to blue. Morganite or rose beryl has a delicate peach-blossom pink tint due to a trace of manganese, while a higher level of manganese produces red beryl. Golden beryl is a clear golden yellow, and heliodor is a greenish-yellow due to a trace of ferrous iron.

Historical Background:

    The Egyptians had to make do with small, inferior green emeralds from the so-called "Cleopatra's emerald mines" in the desolate Gebel Zikait, Gebel Zubara, and Umm Kabo districts of the Red Sea hills, about a hundred miles north of Aswan and 16 miles inland from the Red Sea. Beryl occurs here in quartz pegmatite veins that cut Precambrian talc and mica schists, as well within folded quartz lenses in the schists. Grundmann and Morteani attribute their origin to regional metamorphism and crushing of beryl-rich veins. There is no conclusive evidence that the Egyptians exploited these mines before the Greek epoch (late 4th century BC), when Greek miners sank hundreds of labyrinthine shafts as much as 800 ft into the hillsides. All supposed earlier Egyptian emeralds are amazonite or "mother of emerald," a green variety of microcline feldspar. The Egyptians also prized green turquoise, peridot, chrysacolla, jade, and malachite as symbols of their green farmlands, watered and nourished by the Nile.

    Beryl mining in India began at least as early as 500 BC, if not a millennium or two earlier. Iran and Turkey both have beryl deposits, but these were not exploited before the 4th century BC. Alexander the Great may have obtained his legendary emeralds from mines in the Pansher Valley of Afghanistan, which also supplied Rome with emeralds.

    Beryl is the commercial source of beryllium metal for strong, lightweight alloys, and beryllium oxide (BeO), a refractory material used in spark plugs and insulators. Beryl crystals grow by precipitation from hydrothermal solutions that emanate from the late stages of granitic intrusions into folded mountain belts. The emerald deposits of Muzo and Chivor in Colombia, source of 60% of precious emeralds, formed during the pressure release that occurred when hydrothermal solutions shattered and broke through black shales or grey, calareous shales. The sodium-rich solutions precipitated emeralds in veins of calcite at Muzo and quartz, albite, and apatite at Chivor. Other important modern sources of emeralds include Brazil, the Ural Mountains, Zambia's Miku deposits, and Zimbabwe's Sandawana Valley. The most productive locality for emeralds in the United States was an area around the town of Hiddenite, Alexander County, North Carolina.  It yielded an emerald weighing 1,869 carats, the largest ever found in North America.

    Gaston Guiliani et al recognize three groups of emeralds on the basis of their oxygen isotope ratios and microscopic inclusions. Emeralds from Anagé and Quadilatero Ferrifero in Brazil and from Austria, Australia, and Zimbabwe have low oxygen 18 percentages. Emeralds from Carnaiba and Socoto in Brazil, as well as from Egypt, Madagascar, Kaltharo in Pakistan, Russia, Tanzania, and Zambia have intermediate levels of oxygen 18. Emeralds from Swat-Mingora in Afghanistan, Santa Terezinha de Goias in Brazil, and Colombia contain the highest levels of oxygen 18. These differences proved sufficiently diagnostic to identify the sources of gems in ancient jewels.

 

Sources:

Bartsch, Joel A., Mark Mauthner, and M. Wilson, 2004. Masterpieces of the mineral world: Treasures from the Houston Museum of Natural Science. New York: The Mineralogical Record.

Feininger, Tomas, 1970. Emerald mining in Colombia: History and geology. Mineralogical Record; 1-4: 142-149.

Grundmann, Günter, & Giulio Morteani, 1993. Emerald formation during regional metamorphism: The Zabara, Sikeit and Umm Kabo deposits (Eastern Desert, Egypt). In Thorweihe, Ulf, & Heinz Schandelmeier, eds. Geoscientific Research In Northeast Africa. Rotterdam: A.A. Balkema; 495-498.

Guiliani, Gaston, Marc Chaussidon, Henri-Jean Schubnel, Daniel H. Piat, Claire Rollion-Bard, Christian France-Lanord, Didier Giard, Daniel de Narvaez, & Benjamin Rondeau, 2000. Oxygen Isotopes and Emerald Trade Routes Since Antiquity. Science; 287: 631-633.

Hurlbut, 1952, op. cit.; 376.

Lucas & Harris, op. cit.; 389-390.

O’Donoghue, Michael, ed., 1976. The Encyclopedia of Minerals and Gemstones. New York: G.P. Putnam's Sons.

Ralph, Jolyon, 1993-2004. http://www.mindat.org/min-819.html & http://www.mindat.org//show.php?id=1054

Said, Rushdi, 1962. The Geology of Egypt. Amsterdam & New York: Elsevier, 263.

Schumann, op. cit.; 90-97.

Sinankas, John, & Peter G. Read, 1986. Beryl. London: Butterworths, 2-5, 208.

            Webster, Robert, 1962. Gems. London: Butterworth & Co.; 84.

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