Posted: August 10, 2008 at 4:42 pm
A gem or gemstone is known as a precious or semi-precious stone that is a part of some attractive mineral and used after cutting and polishing to make jewelry and other ornamentation. There are also some rocks and natural materials that are not minerals but still they are used to make jewelry and other ornamentation, i.e. lapis lazuli or amber and jet. These kinds of materials are also considered gemstones. A large number of gemstones are consisted of hard substances but some of them are soft minerals too. A gemologist has to test a wide range of materials as to confirm it as a gemstone. According to some estimates there are almost 270 varieties that have been identified as gemstones.
Gemstones have been using in jewelry and other ornamentation for centuries. Gemstones always have a great amount of attraction in themselves for the people in almost every part of the world. Below is a list of some well-known gemstones with their brief description:
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Posted: August 4, 2008 at 11:42 am
Peridot is usually pronounced as pair-uh-doe and it’s an array of olivine (not a certified mineral) that is consisted of two minerals known as fayalite and forsterite. Fayalite (Fe2Si04) is iron rich while forsterite (Mg2Sio4) is a manganese rich mineral. To show the exchange of magnesium and iron; olivine is chemically formulated as (Mg, Fe) 2Sio4. Though iron serves as a coloring agent for Peridot, yet in composition Peridot is often nearer to forsterite instead of fayalite. A peridot, which has less than 15% of iron and has some trace elements like nickel and chromium, is considered the best in color.
A large number of gemstones that have a mineral origin form in the crust of the earth. But peridot and diamond are two such elements as form deeper in the earth and this deeper region is known as mantle. Peridot crystals are found 20 to 55 miles deeper and they pop up on the surface due to tectonic or volcanic activity. Similarly, diamonds form around 100-150 miles below the surface where temperatures and pressures are extreme.
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