All about Colored Gemstones

Gemstone - is the naturally occurring crystalline form of a mineral, which is desirable for its beauty, valuable in its rarity and durable enough to be enjoyed for generations. The term 'gem material' covers an enormous range of possibilities. Most materials are minerals, but of the 3000 or so minerals known to man, only about 70 are considered to possess the qualities attributed to that special category called 'gemstone'. In general, five basic criterias are used to define what makes a certain material 'gem quality', 1) Beauty 2) Rarity 3) Durability 4) Fashion 5) Portability.
A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive mineral, which - when cut and polished - is used to make jewelry or other adornments. Most gemstones are hard, but some soft minerals are used in jewelry because of their lustre or other physical properties that have aesthetic value.

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Hardness of Gemstones - Hardness is more precisely defined as the ability to resist abrasion as, for example, when a pointed piece of material is drawn across another material without causing either cleavage or fracture. The power a mineral has to resist scratching.
Generally it is desirable that a material should have a hardness of at least 7 on the Moh's scale. This is because of the abrasive action of the millions of dust particles in the atmosphere, composed mainly of quartz, which has a hardness of 7.

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Color in Gemstones - The presence of transition elements such as chromium, titanium, vanadium, iron, magnesium etc., gives rise to color in gemstones that contain them. These elements have the ability to absorb or trap some wavelengths of visible light; and it is a combination of those unabsorbed residual wavelengths that is transmitted to the eye as color. Most gemstones are made up of non-transition elements and are colorless in their purest form. It is the addition of trace percentages of the transition elements that account for the numerous colored varieties of gemstones.

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Inclusion - Is any irregularity observed in a gem - by the unaided eye or (using) some tool such as a hand lens or microscope. The 'irregularity' may be a substance, such as a solid mineral crystal or a fluid filling a cavity, or it may be an unfilled cavity, a fracture, or a growth pattern that produces some optical effect.

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Geology of Gemstone - The earth is a chemical stockpile of atoms of different elements. The stock is being reorganized continually, crystallizing and recrystallizing as minerals and forming and reforming as new rocks. Most gem materials have their origin in the earth's crust. Indeed Gem materials are being formed now within and beneath the earth's crust. These gems crystallize due to pressure, heat and the chemical action of water as it gradually permeates and reacts with the hot solid crust.

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Gemstone Treatment - If the supply of gemstones were limited to those specimens that are naturally attractive, they'd be so expensive that most of us could never own them. Therefore, many gems are treated. A treatment is any process such as heating, oiling, irradiation, waxing, dying or bleaching which alters the color or clarity of a gemstone. Enhancement is often used as another term for treatment.

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Jewelry - is an item of personal adornment, such as a necklace, ring, brooch or bracelet that is worn by a person. It may be made from gemstones or precious metals, but may be from any other material, and may be appreciated because of geometric or other patterns, or meaningful symbols. Earrings and other body rings are also considered to be jewelry,
The word jewelry is derived from the word jewel, which was anglicised from the Old French "jouel" circa the 13th century. Further tracing leads back to the Latin word "jocale", meaning plaything. Jewelry is one of the oldest forms of body adornment.

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Sapphire - Sapphire is one of the two gem varieties of corundum, the other being the red ruby. Although blue is the most well known hue, sapphire is any color of corundum except red. Sapphire may also be colorless, and it also occurs in the non-spectral shades gray and black.
Its chemical formula is aluminium oxide (α-Al2O3), when it is a color other than red, in which case the gem would instead be a ruby. Trace amounts of other elements such as iron, titanium, or chromium can give corundum blue, yellow, pink, purple, orange, or greenish color. Pink-orange corundum are also sapphires, but are instead called padparadscha.
The cost of natural sapphire varies depending on their color, clarity, size, cut, and overall quality as well as geographic origin. Significant sapphire deposits are found in Eastern Australia, Thailand, Sri Lanka, Madagascar, East Africa and in the United States at various locations (Gem Mountain) and in the Missouri River near Helena, Montana.
Sapphires may be treated by several methods to enhance and improve their clarity and color. It is common practice to heat natural sapphires to improve or enhance color. Evidence of sapphire and other gemstones being subjected to heating goes back to, at least, Roman times. Un-heated stones are quite rare and will often be sold accompanied by a certificate from an independent gemological laboratory attesting to "no evidence of heat treatment". Other known treatments are: Diffusion treatments and Surface diffusion treatments.
According to Federal Trade Commission guidelines, in the United States, disclosure is required of any mode of enhancement that has a significant effect on the gem's value.

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Tsavorite Garnet - Green to emerald green variety from Kenya and Tanzania; discovered in the early 1970's. The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives. Tsavorite is a variety of the garnet group species grossular, a calcium-aluminium garnet with the formula Ca3Al2Si3O12.[2] Trace amounts of vanadium or chromium provide the green color.

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Amethyst Quartz - Amethyst is the most highly valued stone in the quartz group. The name means 'not drunken' (Greek), as amethyst was worn as an amulet against drunkenness. Amethyst is the violet variety of quartz; its chemical formula is SiO2.

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Topaz - The name topaz is most probably derived from the island in the Red Sea, now Zabargad but formerly Topazos, the ancient source of peridot. Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO4(F,OH)2. Pure topaz is colorless and transparent but is usually tinted by impurities. Imperial topaz is yellow, pink (rare, if natural) or pink-orange. Brazilian Imperial Topaz can often have a beautiful bright yellow to deep golden brown hue, sometimes even violet. Some imperial topaz stones can fade on exposure to sunlight for an extended period of time.
Naturally occurring Blue Topaz is quite rare. Typically, colorless, gray or pale yellow and blue material is heat treated and irradiated in order to produce a more desired darker blue.

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Gold - is a chemical element with the symbol Au (Latin: aurum) and an atomic number of 79. It has been a highly sought-after precious metal in jewelry, in sculpture, and for ornamentation since the beginning of recorded history. The metal occurs as nuggets or grains in rocks, in veins and in alluvial deposits. Gold is dense, soft, shiny and the most malleable and ductile pure metal known. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water.

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Jewelry Gold - Because of the softness of pure (24k) gold, it is usually alloyed with base metals for use in jewelry, altering its hardness and ductility, melting point, color and other properties. Alloys with lower caratage, typically 22k, 18k, 14k or 10k, contain higher percentages of copper, or other base metals or silver or palladium in the alloy. Copper is the most commonly used base metal, yielding a redder color.

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Silver - is a chemical element with the chemical symbol Ag (Latin: argentum, from the Ancient Greek: ἀργήεντος - argēentos, gen. of ἀργήεντος - argēeis, "white, shining" ) and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal. The metal occurs naturally in its pure, free form (native silver), as an alloy with gold (electrum) and other metals, and in minerals such as argentite and chlorargyrite.

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Sterling Silver - is an alloy of silver containing 92.5% by weight of silver and 7.5% by weight of other metals, usually copper. The sterling silver standard has a minimum millesimal fineness of 925. Fine silver (99.9% pure) is generally too soft for producing large functional objects; therefore, the silver is usually alloyed with copper to give it strength, while at the same time preserving the ductility and beauty of the precious metal.

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Cubic Zirconia (or CZ) - is the cubic crystalline form of zirconium dioxide (ZrO2). Cubic Zirconia is produced in Russia, the same birth place as Tetris. Its synthesized material is hard, optically flawless and usually colorless, but may be made in a variety of different colors. Because of its durability and close visual likeness to diamond, synthetic zirconia has remained the most gemologically and economically important competitor for diamonds since 1976.