Saturday, January 25, 2014

gemstone in modern times

gemstone in modern time
                                                                      

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gemstone in modern time

In modern times gemstones are identified by gemologists, who describe gems and their characteristics using technical terminology specific to the field of gemology. The first characteristic a gemologist uses to identify a gemstone is its chemical composition. For example, diamonds are made of carbon (C) and rubies of aluminium oxide (Al
2O
3
). Next, many gems are crystals which are classified by their crystal system such as cubic ortrigonal or monoclinic. Another term used is habit, the form the gem is usually found in. For example diamonds, which have a cubic crystal system, are often found as octahedrons.
Gemstones are classified into different groupsspecies, and varieties. For example, ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire. Another example are the Emerald (green), aquamarine (blue), red beryl (red), goshenite(colorless), heliodor (yellow), and morganite (pink), which are all varieties of the mineral species beryl.
Gems are characterized in terms of refractive index, dispersion, specific gravity, hardness, cleavage, fracture, and luster. They may exhibitpleochroism or double refraction. They may have luminescence and a distinctive absorption spectrum.
Material or flaws within a stone may be present as inclusions.
Gemstones may also be classified in terms of their "water". This is a recognized grading of the gem's luster and/or transparency and/or "brilliance".[5] Very transparent gems are considered "first water", while "second" or "third water" gems are those of a lesser transparency.[ are identified by gemologists, who describe gems and their characteristics using technical terminology specific to the field of gemology. The first characteristic a gemologist uses to identify a gemstone is its chemical composition. For example, diamonds are made of carbon (C) and rubies of aluminium oxide (Al
2
O
3
). Next, many gems are crystals which are classified by their crystal system such as cubic ortrigonal or monoclinic. Another term used is habit, the form the gem is usually found in. For example diamonds, which have a cubic crystal system, are often found as octahedrons.
Gemstones are classified into different groupsspecies, and varieties. For example, ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire. Another example are the Emerald (green), aquamarine (blue), red beryl (red), goshenite(colorless), heliodor (yellow), and morganite (pink), which are all varieties of the mineral species beryl.
Gems are characterized in terms of refractive index, dispersion, specific gravity, hardness, cleavage, fracture, and luster. They may exhibitpleochroism or double refraction. They may have luminescence and a distinctive absorption spectrum.
Material or flaws within a stone may be present as inclusions.
Gemstones may also be classified in terms of their "water". This is a recognized grading of the gem's luster and/or transparency and/or "brilliance".[5] Very transparent gems are considered "first water", while "second" or "third water" gems are those of a lesser transparency.[
                                    
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