Gemstones, precious and semiprecious stones Precious and semiprecious stones, in addition to gold, silver, and platinum, are the most commonly used components of jewelry. Precious stones: Diamonds have traditionally been the most highly prized of such stones, varying in color from yellow to bluish white and sometimes reaching enormous size. Rubies, emeralds, and sapphires are other precious stones used for jewelry, as are the less costly chrysoberyl, topaz, and zircon. Semiprecious stones: Amethyst, garnet, opal, aquamarine, jade , turquoise, agate, onyx, lapis lazuli, and malachite. Stones of organic origin: Amber, a fossil tree resin, is a highly valued stone. Pearls and corals, though animal in origin rather than mineral, are also usually considered gemstones. Gemstone is any of various minerals highly prized for beauty, durability, and rarity. Of the more than 2,000 identified natural minerals, fewer than 100 are used as gemstones and only 16 have achieved importance. These are beryl, chrysoberyl, corundum, diamond, feldspar, garnet, jade , lazurite, olivine, opal, quartz , spinel , topaz, tourmaline, turquoise, and zircon. Some of these minerals provide more than one type of gem. Beryl, for example, provides emeralds and aquamarines, while corundum provides rubies and sapphires. In virtually all cases, the minerals have to be cut and polished for use in jewelry. Gemstones have attracted humankind since ancient times, and have long been used for jewelry. The prime requisite for a gem is that it must be beautiful. The beauty may lie in color or lack of color, in the latter case, extreme limpidity and "fire" may provide the attraction. A gem must also be durable to withstand the wear and tear of constant handling. In some cases, the color of gemstones is also artificially enhanced (treated gem) to increase the value of the stone. Staining, heat treatment, and irradiation are used among the treatments. Agate may be stained a variety of colors: red, lemon yellow, green, blue, and brown. Jasper stained blue to simulate Lapis Lazuli, and turquoise is stained to imitate opal. Heat treatment of gems to improve or change color has been practiced for centuries. When heated, smoky quartz resembles citrine or topaz, some brownish or reddish zircon becomes bright blue or colorless, yellow topaz becomes pink, slightly colored chalcedony becomes carnelian red, and some rubies or amethysts are more evenly colored. Irradiation of certain gemstones also causes color changes. Some colorless diamonds become green, rose quartz becomes brown, and decolorized amethyst regains its purple hue. These color changes are not always permanent, and the stone may become radioactive. In recent times various kinds of synthetic gems, including rubies, sapphires, and emeralds, have been produced. Two methods of fabrication are currently employed, one involving crystal growth from solution and the other crystal growth from melts. In addition to their use as jewelry, gems were regarded by many civilizations as miraculous and endowed with mysterious powers. Different stones were endowed with different and sometimes overlapping attributes. The diamond, for instance, was thought to give its wearer strength in battle and to protect him against ghosts and magic. During the Middle Ages, a ruby ring was thought to bring its owner lands and titles, to bestow virtue, to protect against seduction, and to prevent effervescence in water--but only if worn on the left hand. Vestiges of such beliefs persist in the modern practice of wearing a birthstone. Agate brings stability to your life. Color: Agate comes in most colors. Agates range from transparent to opaque in a variety of beautiful colors. It presents various tints in the same specimen. The stones can be artificially stained to produce combinations of color more vivid than those found in the natural state. i Description: SiO 2 Agate is a semipellucid crystallized quartz, consisting of banded or with branching inclusions chalcedony . Physical properties of agate are in general those of quartz. Agate has irregular, sometimes circular bands of color and often replaces fossil wood. Many fossils are agatized material where the original organic substance has been replaced by agate while retaining the original structure. Agates are identical in chemical structure to jasper , flint, chert, bloodstone , and tiger-eye , and are often found in association with opal . The colorful, banded rocks are used as a semiprecious gemstone and for making mortars and pestles. One will often see these in beads, agate pendants and necklaces. The name's origin: Agate derives its name from the Greek "Agate??" - happy. According to another theory the word Agate comes from the Greek name of a stone found in the Achates River in Sicily, now known as the Drillo River, which still remains a major source of this stone. Birthstone: Agate is the birthstone of Taurus (Bull): April 20 - May 20. Wedding anniversary: Agate is the anniversary gemstone for the 12th year of marriage. Moss Agate is the anniversary gemstone for the 14th year of marriage. Varieties: There are several types of agate. Varieties include Blue, Blue Lace, Crazy Lace, Green, Indian, Moss, Tree and Wood. The Moss agate or mocha stone contains visible impurities in the form that resemble moss. Care and treatment: Agate will chip and crack rather easily though it has a hardness rating of 7. As with all gems, protect agate from scratches and sharp blows. Avoid sudden temperature changes and household chemicals. From the stone history: Agate was discovered with the Stone Age man in France 20,000-16,000 BC. The Egyptians used it prior to 3000 BC. Agate was highly valued by ancient civilizations. Said by the ancients to render the wearer invisible. The agate-working industry grew up centuries ago in the Idar-Oberstein district of Germany, where agates were abundant. Cameos are cut from stones, such as onyx or agate, where different colors occur in layers. The background material is cut away, leaving the cameo design in relief. Agate is one of the gemstones, that used in commesso , also called florentine mosaic. Commesso is a technique of fashioning pictures with thin, cut-to-shape pieces of brightly colored, semiprecious stones, developed in Florence in the late 16th century. The stones most commonly used are agates, quartzes , chalcedonies , jaspers , granites, porphyries, petrified woods, and lapis lazuli . Commesso pictures, used mainly for tabletops and small wall panels, range from emblematic and floral subjects to landscapes. Healing ability: Agate is cooling stone, it reduces fever, quenches thirst, beneficial in stomach area. It quiets the pulse and heart throbs and insures good health and a long and prosperous life. Botswana Agate: Use with high-pressure oxygen therapy. Fire Agate: Master healer with color therapy, enhances all essences. It grounds and balances, binds sexual & heart chakra, burns energy. Moss Agate: Emotional priorities, mental priorities; circulatory, pancreas & pulses, blood sugar balance, agriculture. Mystical power: Agate guards against danger. Wearers become temperate, continent and cautious. It helps one view themselves with more clarity and see the world through a broader viewpoint. Wearing Agate is believed to cure insomnia and to insure pleasant dreams. Deposits: Important sources of agate are Russia (Ural mountains), Brazil, Eygpt, Germany, India, Italy, Madagascar, Mexico, Uruguay and the USA (Oregon, Washington, Idaho, and Montana ). Alexandrite is a stone of good omen. Color: The best known and most widely used variety of chrysoberyl is an alexandrite. Because of its great power of absorption of certain colors, alexandrite looks green in daylight and reddish purple in artificial light. Description: BeAl2O4 Alexandrite is a remarkable and valued variety of chrysoberyl that when viewed along the different crystallographic (optical) axes, changes from columbine red to orange yellow to emerald green. The name's origin: Alexandrite is named after Czar Alexander's II. Birthstone: Alexandrite along with pearls and moonstone are birthstones of Gemini (Twins): May 21 - June 21. Wedding anniversary: Alexandrite is the anniversary gemstone for the 45th and 55th year of marriage. Care and treatment: Protect alexandrite from scratches, sharp blows, harsh chemicals and extreme temperatures. From the stone history: Alexandrite was discovered in 1831 in the Ural Mountains (Russia) on the Czar Alexander II birthday. Shopping guide: Alexandrite is a beautiful rare stone which is quite expensive. It is very difficult to find natural alexandrite. Most Alexandrites on the market are synthetic. Alexandrite rings are very beautiful. If Alexandrite is set in a ring, the wearer can watch the color change. Healing ability: Alexandrite helps fighting low self-esteem. Improves central nervous system disorders. Alexandrite relieves spleen & pancreas problems. Mystical power: Alexandrite is a stone of good omen. Alexandrite can assist one in centering the self, reinforcing self-esteem, and increases ones ability to experience joy. Deposits: Alexandrite is found in Brazil, Madagascar, Myanmar, Russia, Sri Lanka and Zimbabwe Amazonite makes your married life happier. Stone's names: Amazonite, Amazonstone. Color: Amazonite varies in color from yellow-green to blue-green and may also exhibit fine white streaks. Description: KAlSi3O8 Amazonite is a gemstone variety of green microcline, a feldspar mineral. It is usually opaque and therefore is cut en cabochon (with a rounded and