About Gemstone 

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 Gemstone Information

A gemstone or gem (also called a precious or semi-precious stone, or jewel) is a piece of mineral, which, in cut and polished form, is used to make jewelry or other adornments. However certain rocks, (such as lapis lazuli) and organic materials (such as amber or jet) are not minerals, but are still used for jewelry, and are therefore often considered to be gemstones as well.

Most gemstones are hard, but some soft minerals are used in jewelry because of their lustre or other physical properties that have aesthetic value. Rarity is another characteristic that lends value to a gemstone. Apart from jewelry, from earliest antiquity until the 19th century engraved gems and hardstone carvings such as cups were major luxury art forms; the carvings of Carl Fabergé were the last significant works in this tradition. Some of the popular gemstones are :

 
  • Alexandrite
  • Amber
  • Amethyst
  • Ametrine
  • Ammolite
  • Aquamarine
  • Beryl
  • Chalcedony
  • Chrome Diopside
 
  • Chrysoberyl
  • Chrysoprase
  • Citrine
  • Coral
  • Diamond
  • Emerald
  • Garnet
  • Iolite
  • Jade
 
  • Kunzite
  • Lapis Lazuli
  • Moonstone
  • Morganite
  • Onyx
  • Opal
  • Pearl
  • Peridot
  • Phenomenal
 
  • Ruby
  • Sapphire
  • Spinel
  • Sunstone
  • Tanzanite
  • Topaz
  • Tourmaline
  • Turquoise
  • Zircon

 

Anniversary Gemstones

       
  • 1st Anniversary : Gold Jewelry
  • 2nd Anniversary : Garnet
  • 3rd Anniversary : Cultured/Natural Pearls
  • 4th Anniversary : Blue Topaz
  • 5th Anniversary : Sapphire
  • 6th Anniversary : Amethyst
  • 7th Anniversary : Onyx
  • 8th Anniversary : Tourmaline
  • 9th Anniversary : Lapis Lazuli
  • 10th Anniversary : Diamond Jewelry
  • 11th Anniversary : Turquoise
  • 12th Anniversary : Jade
  • 13th Anniversary : Citrine
  • 14th Anniversary : Opal
  • 15th Anniversary : Ruby
  • 16th Anniversary : Peridot
      
  • 17th Anniversary : Watches
  • 18th Anniversary : Cat’s Eye
  • 19th Anniversary : Aquamarine
  • 20th Anniversary : Emerald
  • 21st Anniversary : Iolite
  • 22nd Anniversary : Spinel
  • 23rd Anniversary : Imperial Topaz
  • 24th Anniversary : Tanzanite
  • 25th Anniversary : Silver Jubilee
  • 30th Anniversary : Cultured/Natural Pearl
  • 35th Anniversary : Emerald
  • 40th Anniversary : Ruby
  • 45th Anniversary : Sapphire
  • 50th Anniversary : Golden Jubilee
  • 55th Anniversary : Alexandrite
  • 60th Anniversary : Diamond

Birthstones

January : Garnet

February : Amethyst

March : Aquamarine or Bloodstone

April : Diamond

May : Emerald

June : Pearl, Moonstone or Alexandrite

July : Ruby

August : Peridot

September : Sapphire

October : Opal or Tourmaline

November : Topaz or Citrine

December: Turquoise, Zircon or Tanzanite

 

 

 

 

 Value of gemstones

There is no universally accepted grading system for gemstones. Diamonds are graded using a system developed by the Gemological Institute of America (GIA) in the early 1950s. Historically, all gemstones were graded using the naked eye. The GIA system included a major innovation: the introduction of 10x magnification as the standard for grading clarity. Other gemstones are still graded using the naked eye .

A mnemonic device, the "four Cs" (colour, cut, clarity and carats), has been introduced to help the consumer understand the factors used to grade a diamond. With modification, these categories can be useful in understanding the grading of all gemstones. The four criteria carry different weight depending upon whether they are applied to colour gemstones or to colourless diamond. In diamonds, cut is the primary determinant of value, followed by clarity and colour. Diamonds are meant to sparkle, to break down light into its constituent rainbow colours (dispersion), chop it up into bright little pieces (scintillation), and deliver it to the eye (brilliance). In its rough crystalline form, a diamond will do none of these things; it requires proper fashioning and this is called "cut". In gemstones that have colour, including colour diamonds, it is the purity and beauty of that colour that is the primary determinant of quality.

Physical characteristics that make a colour stone valuable are colour, clarity to a lesser extent (emeralds will always have a number of inclusions), cut, unusual optical phenomena within the stone such as colour zoning, and asteria (star effects). The Greeks, for example, greatly valued asteria in gemstones, which were regarded as a powerful love charm, and Helen of Troy was known to have worn star-corundum.

Historically, gemstones were classified into precious stones and semi-precious stones. Because such a definition can change over time and vary with culture, it has always been a difficult matter to determine what constitutes precious stones.

Aside from the diamond, the ruby, sapphire, emerald, pearl (strictly speaking not a gemstone) and opal have also been considered to be precious. Up to the discoveries of bulk amethyst in Brazil in the 19th century, amethyst was considered a precious stone as well, going back to ancient Greece. Even in the last century certain stones such as aquamarine, peridot and cat's eye have been popular and hence been regarded as precious.

Nowadays such a distinction is no longer made by the trade. Many gemstones are used in even the most expensive jewelry, depending on the brand name of the designer, fashion trends, market supply, treatments etc. Nevertheless, diamonds, rubies, sapphires and emeralds still have a reputation that exceeds those of other gemstones.

Rare or unusual gemstones, generally meant to include those gemstones which occur so infrequently in gem quality that they are scarcely known except to connoisseurs, include andalusite, axinite, cassiterite, clinohumite and red beryl.

Gem prices can fluctuate heavily (such as those of tanzanite over the years) or can be quite stable (such as those of diamonds). In general per carat prices of larger stones are higher than those of smaller stones, but popularity of certain sizes of stone can affect prices.

 

Gemstone color

Color is the most obvious and attractive feature of gemstones. The color of any material is due to the nature of light itself. Daylight, often called white light, is actually a mixture of different colors of light. When light passes through a material, some of the light may be absorbed, while the rest passes through. The part that is not absorbed reaches the eye as white light minus the absorbed colors. A ruby appears red because it absorbs all the other colors of white light (blue, yellow, green, etc.) except red.

The same material can exhibit different colors. For example ruby and sapphire have the same chemical composition (both are corundum) but exhibit different colors. Even the same gemstone can occur in many different colors: sapphires show different shades of blue and pink and "fancy sapphires" exhibit a whole range of other colors from yellow to orange-pink, the latter called "Padparadscha sapphire".

This difference in color is based on the atomic structure of the stone. Although the different stones formally have the same chemical composition, they are not exactly the same. Every now and then an atom is replaced by a completely different atom (and this could be as few as one in a million atoms). These so called impurities are sufficient to absorb certain colors and leave the other colors unaffected.

For example, beryl, which is colorless in its pure mineral form, becomes emerald with chromium impurities. If you add manganese instead of chromium, beryl becomes pink morganite. With iron, it becomes aquamarine.

Some gemstone treatments make use of the fact that these impurities can be "manipulated", thus changing the color of the gem.

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W.E.F. 1 Jun 2011