13 Mart 2013 Çarşamba

North Carolina State Gemstone

North Carolina State Gemstone

Emerald

STATUS
Official
DESCRIPTION
Emerald is a beryllium aluminum silicate. It is a medium green, dark green, or blue-green gem-quality variety of the mineral beryl, and the most precious stone in the beryl group. Pure beryl is white; trace amounts of impurities such as chromium, and sometimes iron or vanadium give emerald its color. Aquamarine, morganite, and heliodor are beryls of other colors.
STATE SYMBOL
More than 300 minerals have been found in North Carolina—more than any other state. A 1,869-carat emerald crystal found near Statesville, North Carolina, in 2003 is thought to be the largest ever found in North America. A 71-carat crystal found at the same site yielded two finished stones: the 7.85-carat Carolina Prince (which sold for $500,000) and the 18.88-carat Carolina Queen. North Carolina designated emerald its official state precious stone in 1973.
NAME ORIGIN
The word emerald comes via the Old French word esmeraldefrom Latin smaragdusand Greek smaragdos (σμάραγδος), its original source possibly being the Semitic word izmargad or the Sanskrit word, marakata, meaning "emerald" or simply "green gemstone."
FORMATION AND OCCURRENCE
Beryls occur in granites and granite pegmatites and rarely in granular igneous rocks. They are also found in dark-colored metamorphic rocks composed of iron and magnesium, in low- to high-temperature hydrothermal mica schist veins, and in cavities in rhyolite. Emeralds occur with pyrite, calcite, and quartz.
GEOGRAPHIC DISTRIBUTION
In antiquity, emeralds were mined in Egypt, Austria, and northern Pakistan. Today, the majority of the world’s gem-quality emeralds come from the Muzo, Chivor, and Coscuez mines in Colombia. The stone was discovered in Yukon Territory, Canada, in 1998. The following is a list of countries with emerald deposits.

  • Afghanistan
  • Australia
  • Austria
  • Brazil
  • Bulgaria
  • Canada
  • China
  • Colombia
  • Egypt
  • Ethiopia
  • France
  • Germany
  • India
  • Italy
  • Kazakhstan
  • Madagascar
  • Mozambique
  • Namibia
  • Nigeria
  • Norway
  • Pakistan
  • Russia
  • Somaliland
  • South Africa
  • Spain
  • Switzerland
  • Tanzania
  • United States
  • Zambia
  • Zimbabwe
FAMOUS EXAMPLES
The Bahia Emerald is one of the largest emeralds ever found, at 180,000 carats. It was found in Brazil and in 2008, was reported stolen from Los Angeles. It was recovered in December 2008, but is being held by police until one of the five people claiming ownership can be determined the rightful owner.
One of the largest gem emeralds in the world, the Gachalá Emerald is 858 carats. It was found in 1967 in Gachalá, Colombia and now resides at the National Museum of Natural History in Washington, DC. The American Museum of Natural History in New York has an exhibit in which a cup made of emerald that once belonged to Emperor Jehangir sits next to the 632-carat "Patricia," one of the largest Colombian emerald crystals.
Queen Elizabeth II’s personal jewelry collection includes the "Cambridge and Delhi Dunbar Parure," an incredible suite of emerald jewelry that includes an emerald crown.
Elizabeth Taylor’s famous jewelry collection includes the emerald and diamond engagement brooch she received from Richard Burton, the emerald necklace he gave her as a wedding present, and the emerald earrings, ring, and bracelet he later purchased for her.
USES
Historical Uses
Emeralds have been prized as gems for thousands of years. The oldest known stones come from mines near the Red Sea in Egypt. Incas and Aztecs regarded the gemstone as holy, and Aztecs mined today’s important deposits at Muzo and Chivor, Colombia. The Vedas, the holy scriptures of the Indians written thousands of years ago, say that emeralds bring good luck and well-being.
Modern Uses
Emeralds are highly sought after as gemstones. Fine emeralds are even more valuable than diamonds. Transparent emeralds are faceted, and this gem has even had a cut named after it. Translucent specimens are cut into cabochons and beads. Deep, dark- to medium-green color and high transparency create the highest value stones.
As with all gemstones, flawless specimens also command higher prices. In the case of emeralds, however, flawless gems are extremely rare. Traditionally, cracks were filled in with oil. Oil-treated emeralds should not be cleaned with soap or steam or in ultrasonic cleaners, as those techniques can remove the oil, thus revealing the gem’s flaws. Fracture-filling techniques, such as with a permanent epoxy, and irradiation are more commonly used today to remove some flaws. The U.S. Federal Trade Commission requires jewelers to disclose treatments to customers, but oil and resin treatments are considered acceptable, unless they are used to change the gem’s color.
Legend
Emerald amulets were once worn to protect from eye diseases and epilepsy. The color green represents spring, nature, life, and harmony. In ancient Rome, green was the color of Venus, the goddess of beauty and love. Green is the holy color of Islam and is considered the most natural and most elemental of the liturgical colors in Catholicism. Emeralds are said to enhance love and contentment.
BIRTHSTONE
Emerald is the traditional and modern birthstone for May and for the zodiac signs Taurus and Cancer. It is also the planetary stone for Taurus and the talismanic stone for Gemini. Emeralds are given to commemorate the 20th and 35th wedding anniversaries.
SUBSTITUTES / SYNTHETICS
Synthetic emeralds have been produced since 1848. These stones, as well as faceted green glass, are extremely difficult to distinguish from authentic gems. Because of this, some people actually prefer emeralds with some inclusions to prove their authenticity. Inclusions in emeralds are perhaps tolerated more than in any other gem.
Diopside and dioptase may resemble emerald, but are softer. Green sapphire may also resemble emerald, but is harder. Green tourmaline can be distinguished from emerald only by its unique optical properties.

State Gemstone
Rough Emerald Sample in Rock
State Gemstone
Emerald Crystals Take Shape
State Gemstone
Unfinished Emerald Next to Cut Emerald
State Gemstone
Emerald Setting
EMERALD FACTS
Group: Cyclosilicates
Chemical Formula: Be3Al2(SiO3)6::Cr
Crystal Structure: Hexagonal
Hardness (Mohs): 7.5-8.0
Color: Green
Luster: Vitreous
Pleochroism: Definite
Refractive Index: 1.576-1.582
Density: 2.67-2.78
Streak: White
Cleavage: Poor basal cleavage (seldom visible)
Fracture: Conchoidal


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

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