Thursday, November 27, 2008
Precious stones, also known as gemstones, are minerals or rocks that that turn into collectible when they are cut or faceted and polished. In addition, precious stones are used in jewels.
Precious stones can occur naturally, or they can be laboratory virtual. Natural precious stones come directly out of the ground or mine and are cut or faceted to the preferred shape and size. These precious stones are generally the most popular among collectors and consumers, as well as the most expensive. Laboratory fake precious stones are created in a lab. These manmade stones can still be considered precious stones, but are easier to come by and usually less cost than their natural counterparts.
There are also natural precious stones. Amber, which is made from fossilized tree resin, is an instance of an organic precious stone. Jet, which is a form of coal, is one more organic precious stone. There are some precious stones that are too soft or flimsy to be used in jewelry, such as single-crystal rhodochrosite. Though these precious stones cannot be used for jewelry, they are exhibited in museums and sought by collectors because of their beauty.
Gemologists use technical condition to differentiate precious stones. The foremost consideration when identifying precious stones is the chemical composition. Diamonds, for instance, are made of carbon, and rubies are made of aluminum oxide. Most precious stones are really crystals, which are classified by a crystal system as cubic, trigonal, or monoclinic.
Precious stones are also classified into different groups, class, and varieties. The ruby, for example, is the red mixture of the species corundum, which belongs to the spinel or hematite group. The emerald, aquamarine, bixbite, goshenite, heliodor, and morganite, in addition, are all varieties of the mineral species beryl.
Sorting out precious stones into these types of groups helps to identify their composition, their color, and their origin. Precious stones also have a refractive index, dispersion, exact gravity, hardness, cleavage, fracture, and lustre. Each of these features is significant when assessing the value of the stone.
Precious stones can occur naturally, or they can be laboratory virtual. Natural precious stones come directly out of the ground or mine and are cut or faceted to the preferred shape and size. These precious stones are generally the most popular among collectors and consumers, as well as the most expensive. Laboratory fake precious stones are created in a lab. These manmade stones can still be considered precious stones, but are easier to come by and usually less cost than their natural counterparts.
There are also natural precious stones. Amber, which is made from fossilized tree resin, is an instance of an organic precious stone. Jet, which is a form of coal, is one more organic precious stone. There are some precious stones that are too soft or flimsy to be used in jewelry, such as single-crystal rhodochrosite. Though these precious stones cannot be used for jewelry, they are exhibited in museums and sought by collectors because of their beauty.
Gemologists use technical condition to differentiate precious stones. The foremost consideration when identifying precious stones is the chemical composition. Diamonds, for instance, are made of carbon, and rubies are made of aluminum oxide. Most precious stones are really crystals, which are classified by a crystal system as cubic, trigonal, or monoclinic.
Precious stones are also classified into different groups, class, and varieties. The ruby, for example, is the red mixture of the species corundum, which belongs to the spinel or hematite group. The emerald, aquamarine, bixbite, goshenite, heliodor, and morganite, in addition, are all varieties of the mineral species beryl.
Sorting out precious stones into these types of groups helps to identify their composition, their color, and their origin. Precious stones also have a refractive index, dispersion, exact gravity, hardness, cleavage, fracture, and lustre. Each of these features is significant when assessing the value of the stone.
posted by tamilselvi @ 4:14 AM
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Tuesday, November 18, 2008
The production of gem-quality sapphires in the United States is not new or recent. In 1865, the first U.S. sapphires were found in the gravels of the Missouri River in Lewis and Clark County, Montana. This was followed by subsequent discoveries on Dry Cottonwood Creek in Deer Lodge County in 1889, on Rock Creek in Granite County in 1892, and in Yogo Gulch in Judith Basin County in 1895. Additionally, small amounts of sapphire are recovered from Quartz Gulch in Granite County, Pole Creek in Madison County, the Missouri River in Chouteau County, and Brown's Gulch in Silver Bow County. Furthermore, corundum crystals, from which star sapphires have been cut, are found in Beaverhead and Madison Counties. Also, in 1895, the first sapphires were produced from the Cowee Valley in Macon County, North Carolina. But until very recently, with the exception of Yogo Gulch material, the commercial gemstone industry has had limited interest in U.S. sapphires.
Montana.--Mining of Yogo Gulch sapphires began within a year of their discovery in 1895 and continued for 39 years. In 1923, the mine was damaged so badly by rain that it could not economically recover. Other attempts have been made to commercially mine the deposit, but to date, all of these attempts have ended in economic failure.
Yogo's are unique among the world's sapphires. They lack the color zoning so prevalent in other sapphires, their uniform "corn-flower blue" color is natural (not the result of heat-treating), and their clarity is uniformly high. These features rank them among the world's finest sapphires. Unfortunately, the rough is both small and flat, wafer-like in shape. The majority of the crystals or pieces of crystals recovered are too small to be cut, most are less than 1 carat and finds of over 2 carats are rare. Reportedly, the largest crystal was a 19 carat stone found in 1910 that was cut into an 8-carat stone. The size of the cut stones greatly restrict the market for Yogo's, they are beautiful, small, very expensive sapphires.
Currently, Yogo sapphires are produced from three sources: Rancor lnc., produces material from the original Yogo Gulch deposit; Vortex Mining produces from a recently discovered extension of the Yogo dike; and material is produced by individuals from privately owned lots in Sapphire Village. The first two producers market only cut stones and finished goods and the third is comprised essentially of hobbyists.
Montana.--Mining of Yogo Gulch sapphires began within a year of their discovery in 1895 and continued for 39 years. In 1923, the mine was damaged so badly by rain that it could not economically recover. Other attempts have been made to commercially mine the deposit, but to date, all of these attempts have ended in economic failure.
Yogo's are unique among the world's sapphires. They lack the color zoning so prevalent in other sapphires, their uniform "corn-flower blue" color is natural (not the result of heat-treating), and their clarity is uniformly high. These features rank them among the world's finest sapphires. Unfortunately, the rough is both small and flat, wafer-like in shape. The majority of the crystals or pieces of crystals recovered are too small to be cut, most are less than 1 carat and finds of over 2 carats are rare. Reportedly, the largest crystal was a 19 carat stone found in 1910 that was cut into an 8-carat stone. The size of the cut stones greatly restrict the market for Yogo's, they are beautiful, small, very expensive sapphires.
Currently, Yogo sapphires are produced from three sources: Rancor lnc., produces material from the original Yogo Gulch deposit; Vortex Mining produces from a recently discovered extension of the Yogo dike; and material is produced by individuals from privately owned lots in Sapphire Village. The first two producers market only cut stones and finished goods and the third is comprised essentially of hobbyists.
posted by tamilselvi @ 1:06 AM
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