2 Nisan 2013 Salı

Rhode Island State Gemstone

Rhode Island State Gemstone


Amethyst is the most precious variety of quartz. Composed of silicon dioxide, amethyst is colored light pinkish violet to deep purple by iron and aluminum impurities.
Rhode Island does not have an official state gemstone, but since a number of deposits yielding high-quality amethyst occur statewide, this stone represents the state’s geology well. Rhode Island has been known for gem-quality amethyst from Bristol Ferry since the 1820s, and Bristol amethyst was displayed in the Rhode Island exhibit at the Philadelphia Centennial in 1876. Notable deposits in Rhode Island include Burrillville, Cumberland, Westerly, Providence, Smithfield, and Hopkinton.
In 1981, amethyst scepter overgrowths on milky quartz were discovered at Ashaway Village, Hopkinton, Rhode Island. Well-formed specimens from this rare occurrence became instant classics and some of the most desirable pieces among American mineral collectors. Some of the most remarkable specimens collected at this site, which is now closed to the public, currently reside in Washington, DC’s National Museum of Natural History, New York City’s American Museum of Natural History, and the Harvard Mineralogical Museum in Cambridge, Massachusetts.
South Carolina designated amethyst its official gemstone in 1969. Amethyst is one of two varieties of quartz designated official gemstones of Georgia.
The name for this stone comes from the Greek á- (not) andmethustos (intoxicated), a reference to the belief that the stone protected its owner from drunkenness.
Amethyst occurs in crystalline or massive forms. This stone can occur as six-sided crystals or as drusy, which are crystalline crusts covering the host rock. It is found in alluvial deposits and inside geodes all over the world. Fine specimens are found in Maine and Rhode Island as well as in Georgia and Maryland, the two states which have designated amethyst as a state stone.
  • Mexico: Piedras Parado and Las Vigas de Ramirez, Veracruz; and Amatitlan, Guerrero
  • Brazil: Minas Gerais, Rio Grande do Sul, Maraba
  • Uruguay: Artigas
  • Bolivia: Anahi Mine, Santa Cruz
  • Russia: Ural Mountains and Siberia
  • South Korea
  • India
  • Zambia
  • Namibia: Goboboseb Mountains, near Brandberg, in the Erongo Mountains
  • South Africa: Magaliesberg Mountains in Pretoria and Boekenhoutshoek area in the Mkobola district
  • Canada: Thunder Bay, Ontario and Digby, Nova Scotia
  • United States: Four Peaks (Mazatzal Mountains), Gila and Maricopa Counties, Arizona; Pohndorf Mine, Jefferson County, Montana; Pennoyer Mine at Redfeather Lakes, Larimer County, Colorado; Amethyst Mountain, Texas; Yellowstone National Park; Diamond Hill in Ashaway, Hopkinton, Washington County, Rhode Island; Statesville, Iredell County, North Carolina; the Reel Mine, Iron Station, Lincoln County, North Carolina; Haywood County, North Carolina; Abbeville County, South Carolina; Wilkes County, Georgia; Paterson and Prospect Park, Passaic County, New Jersey; Delaware County, Pennsylvania; Deer Hill and Stow, Maine
Historical Uses
A favorite of Egyptian and British royalty, amethysts are featured in the British Crown Jewels. The gem was also called "the stone of bishops," as it was prized in the high ranks of the Catholic Church. Since ancient Greeks and Romans believed amethyst would prevent intoxication, they wore amethyst and made wine goblets from the stone. Ancient Egyptians used amethyst in engraved intaglios.
Modern Uses
Formerly considered a precious gem, amethyst lost much of its status and value once large deposits were discovered. However, it remains prized for its beautiful color. Because amethyst is very common, it is an inexpensive and widely used stone. Most amethyst is faceted into gemstones, and is sometimes cut into cabochons. The best gems are transparent and free of visible inclusions. Large, massive chunks of amethyst banded with quartz are sometimes carved into ornaments. Collectors look for geodes, tumbled stones, and rare prismatic crystals. The rarest stones, called Deep Russian, are very valuable.
Heating can enhance amethyst’s purple color or turn it yellow-brown to dark brownish. Much of the citrine, a yellow to brown variety of quartz, and smoky quartz sold in jewelry today are artificially formed by heat-treating amethyst.
In Greek mythology, Dionysus, the god of wine, ritual madness, and ecstasy, was pursuing a maiden named Amethystos. She refused his advances and prayed to the god Artemis to keep her chaste. Artemis answered her by turning her into a white stone. Dionysus then poured wine over Amethystos, turning the crystals purple. Another variation says that the goddess Rhea, "the mother of gods," gave Dionysus the amethyst stone to preserve the wine-drinker’s sanity.
Amethyst is said to be of help for headaches, the pancreas, hearing disorders, insomnia, and backache. Because of its connection to wine and sobriety, it is said to be helpful in overcoming addiction.
Amethyst is the traditional birthstone for February and the stone for the zodiac sign of Pisces. This gem is the planetary stone of Neptune. Amethyst is suggested as a gem to give on the fourth, sixth, and 17th wedding anniversaries.
Synthetic amethyst has chemical and physical properties so similar to genuine amethyst that without expensive gemological testing, they cannot be differentiated.
State Gemstone
Purple Amethyst Crystals
State Gemstone
Polished Amethyst Stones
State Gemstone
Finished Cut Amethyst Gemstone
Group: Quartz
Chemical Formula: SiO2
Crystal Structure: Trigonal
Hardness (Mohs): 7, lower in impure varieties
Color: Purple to white 
Transparency: Transparent
Luster: Vitreous
Birefringence: +0.009 (B-G interval)
Pleochroism: None
Refractive Index: 1.544-1.553 - Dr +0.009 (B-G interval)
Density: 2.65 constant; variable in impure varieties
Streak: White
Cleavage: None
Fracture: Conchoidal

Some data courtesy of the Mineralogical Society of America.
Author: World Trade Press

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