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.

There are only few gemstones that come in one color and Peridot is one of them. The deep effects of green color depend on iron composition in crystal formation and it also fluctuates from yellow-green to olive and brownish-green. Peridot is also called poor man’s emerald. No doubt, olivine is abundantly found mineral but still gemy peridot is rare in fact.

Peridots are abundantly found in Burma, Pakistan, China, Vietnam, and the U.S. The finest quality of Peridot is found in Burma and Pakistan while the U.S is considered the largest producer of peridot in the world. A large part of American peridot comes from the deposits of Arizona. A locality known as Peridot Mesa, which is situated on the San Carlos Apache Indian Reservation east of Globe in Gila County, is considered the largest productive locality of peridot all around the globe. Almost 80 to 90 percent of peridot in the world is produced by San Carlos Reservation.

The largest cut peridot has been found as weighed around 310 carats and placed in Washington D.C. at Smithsonian. Similarly in the Diamond treasury Moscow there is a 192.75 carat peridot that belongs to czars. A 146 carat peridot is found in the geological Museum in the city of London. When it is small in sizes, it is considered relatively less expensive gemstone but its value considerably increases if the stone is over 5 carats. Peridot with 10-15 carats weight is rare and that’s why quite expensive. Peridot is always counted an untreated gem as there isn’t any known treatment that is used to enhance color or clarity of peridot. People born in the month of August must regard peridot as it’s birthstone for this month.

Related Links

• http://en.wikipedia.org/wiki/Peridot
• Peridot at DeMairo.com

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These organic gems are not found in a wide range but they include some usual varieties that are considered very important in the gem business. Amber, coral, jet, ivory and pearl are some member of this organic gem family.

Amber is considered as the fossilized toughen organic substance of the pine tree that came into being almost 50 million years back. The use of amber in jewelry, religious objects and amulets is as old as hills; it has been used in these things since prehistoric times. There is addition of insects, plants or pyrites in the pieces of amber which are considered the most prized. Kaliningrad in Russia is the place where the largest deposits of amber are found in the world. There are also large reserves of the amber in the seabed of the Baltic.

Coral is counted as a branching skeleton-like formation that used to build by small sea animals that were called as coral polyps. Reef-forming corals are the workers behind forming gem-quality coral. Mediterranean, Red sea and coastal plans in Japan are the places where the most valuable coral variety is found. Bright to dark, red to orange-red pink, white black and blue are some well-known color ranges of Corals. Unpolished coral is dull but once it shines it gives an attractive glassy luster.

During 19nth century Jet was very popular but it’s quite unique. A bituminous coal that can be polished is called a Jet. Jet’s fame is related to Queen Victoria of England who wore jet as her mourning after Prince Albert’s death. Due to its light weight long necklaces of jet beads were popular enough among the women during 1920s.

Usually, the material of elephant’s tusk is referred to Ivory but these days teeth of hippopotamus, walrus, wild boar and some other mammals also serve as ivory. Ivory, just like bones, is consisted of calcium phosphate. In the past when plastic wasn’t commonly found, cutlery handles, billiards balls, some musical instruments and carved ornamental items were formed with ivory. But many animals that have ivory tusk were killed to get their tusk and that was the reason that import and sale of ivory was strictly banned in many countries of the world.

Pearl is considered the king of all organic gems. The use of pearls was quite obvious even more than 6000 year back. There was a considerable pearl trade in China even by 2500 B.C.

The best quality of pearl is that they need not any processing the give their best unique features and full luster in their natural state. Pearls are grown or cultivated in hinged shell mollusks of the oyster type. Pearl are widely searched in different seas and streams.

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To gauge the hardness or resistance against scratch of many minerals, German mineralogist Friedrich Mohs developed a scale in 1822 and later this scale was named as Moh’s scale. This scale was based on ten readily available minerals. Moh scale is a position showing scale and you have to put two minerals on comparison to know what mineral is comparatively hard.

On this scale diamond and corundum are rated at ten that prove that they have the ability to scratch all other listed gems: while topaz at nine, quartz at eight, orthoclase at seven, apatite at six, fluorite at 5, calcite at four, gypsum at third, and talc at second .This list shows that topaz has the ability to scratch all these gems that have lower ratings than topaz while it can be scratched by diamond or corundum.

It is worth mentioning that Mohs scale only gives relative measurement as it can’t tell anything about how much harder diamond is than other gemstones like topaz or quartz.

It is not right to judge the durability of the gemstone only through its hardness; just hardness can’t be a proof of some gemstone’s durability.  For instance, a perfect cleavage is found in the diamond which means it can be broken with a single waft. The same is the case with topaz which is another very hard gem.

Ruby and sapphire are not as hard as diamond but they have no cleavage and the same quality is found in spinal and quartz. Some other gems like emerald are quite hard but they have internal cleavages that often filled by polishing and oiling. Contrarliy, some gems like jade are not hard enough but still very tough due to their specific crystal structure.

Stability is another thing to measure durability. The tendency of a material to be altered as a reaction of heat, light or chemicals is counted as its stability. Some gemstones like aquamarine and peridot must not be contacted with acids. Similarly some gemstones like kunzite, hiddentie and brownish-yellow topaz fade when they are exposed to the sun for long periods of time. Some gems that surround water like opals have the tendency to become crack and dehydrated.

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Lapis lazuli was used as a gemstone material even many thousands years back. Assyrians and Babylonians used it for cylinder seals while ancient Egyptian used it for sacred slabs and amulets. According to many historians, pulverized lapis was used as an eye shadow by Cleopatra. It was also used in buildings and statues, beads, jewelry and many other things.

During the medieval period, powdered lapis was used in paintings for a blue hue known as ultramarine. But in the early 19th century the synthetic version of ultramarine was found and the use of lapis for paintings declined.

Lapis is considered a rock instead of a mineral as it is consisted of more than one mineral and usually 3 mineral are found in the lapis and they are lazurite, calcite and pyrite. In Lazurite, sulfur is excessively found and it gives a vivid blue color to the lapis. In Calcite there is calcium carbonate that gives a whitish streak to the Lapis.  Iron sulfide is found in Pyrite that is of white-gold color and lends lapis a distinctive sleek and gloss.

The lapis which considered the most expensive one has a deep blue intense in it. It has smooth and fine grained surface and has least amount of calcite. Most often the collectors prefer to those lapis as has no calcite. The calcite gives a white streak or spots to the darker blue stone. The most preferable lapis for the collectors is one that includes high amounts of pyrite but this inclusion too must be within a limit and not in too large. Pyrite has the tendency to discolor lapis at the edges.

Lapis ranges 5 to 6 on the Mohs scale and that is why it’s a rather soft stone. It also has the tendency to absorb the different other chemicals from the surroundings and that’s why it must be protected from solvents and chemicals. Most of the times Lapis are cut as cabochons or beads and used I a number of ornamental objects. These days are also many other blue gemstones but the original one is lapis. Because of it’s unique blue color it is also called the stone of the sky.

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