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Birthstone Chart |
| January: Garnet | February: Amethyst | March: Aquamarine, Bloodstone | April: Diamond , White Topaz |
| May: Emerald | June: Pearl, Alexandrite, Rhodalite Garnet | July: Ruby | August: Peridot |
| September: Sapphire | October: Opal, Pink Tourmaline | November: Citrine, Topaz | December: Blue Topaz, Tanzanite, Zircon, Turquoise |
Jewelry (the American spelling; spelled jewellery in Commonwealth English) consists of ornamental devices worn by persons, typically made with gems and precious metals. Costume jewelry is made from less valuable materials. However, jewelry can and has been made out of almost every kind of material.
The word is derived from the word "jewel", which was anglicised from the Old French "jouel" in around the 13th century. Further tracing leads back to the Latin word "jocale", meaning plaything.
Jewelry, particularly when made with precious materials, is generally considered valuable and desirable. Some cultures have a practice of keeping large amounts of wealth stored in the form of jewelry. Jewelry can also be symbolic, as in the case of Christians wearing a crucifix in the form of jewelry, or, as is the case in many Western cultures, married people wearing a wedding ring.
Jewelry in various forms has been made and worn by both sexes in almost
every (if not every) human culture, on every inhabited continent. Personal
adornment
seems to be a basic human tendency.
Common types
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Less common types |
Special functions
Components |
This is a jewelry timeline from the first uses of metal in history to the Renaissance.
7000 BC - Uses of copper in Anatolia, Iran and Eastern Europe.
3000 BC - The Middle East employ semi-mass-production
2000 BC - First signs of the swagging technique
2500 BC - True iron production technology in Near East.
2500 BC - The intentional addition of silver and copper to gold.
2500 BC - Gold wires are characterised by seam lines that follow a spiral path along the wire.
1500 BC - Earplugs and earrings become popular in Egypt.
1400 BC - Egypt Amarna period, using resin and mud for repoussé backing.
1400 BC - Deliberate addition of zinc to copper in Canaan.
1400 BC - Philistines have iron.
1400 BC - Very copper rich gold alloys popular in Egypt.
1000 BC - The start of true engraving.
575 BC - In Greece, jewelry is still very rare.
500 BC - Hafted hammers were being used in some parts.
500 BC - Iron in use in Britain
325 BC - Animal or human-headed hoop earrings were popular.
AD 50 - Start of the Roman period, where addition of silver to gold becomes almost unknown.
AD 100 - Sulphur fills hollow gold items throughout the Roman Empire.
AD 400 - A shale die is found in Britain.
AD 1500 - The Renaissance
Tanzanite is the blue/purple variety of the mineral zoisite discovered in the Meralani Hills of northern Tanzania in 1967, near the city of Arusha. It is a popular and valuable gemstone when cut, although its durability is somewhat lacking. Tanzanite is noted for its remarkably strong trichroism, appearing alternately sapphire blue, violet, and sage-green depending on crystal orientation. However, most tanzanite is subjected to artificial heat treatment to improve its colour: this significantly subdues its trichroism.
The name tanzanite was a trade name coined by Tiffany & Co. shortly after the gem's discovery, an obvious allusion to its country of origin. This was thought necessary in order to make the stone marketable to the public: the name has since stuck as a varietal designation. Tanzanite's present-day popularity as a gemstone is largely thanks to Tiffany's marketing campaigns. The mining of tanzanite nets the Tanzanian government approximately USD $20 million annually, the finished gems later being sold mostly on the US market for sales totaling approximately USD $500 million annually.
In June of 2003, the Tanzanian government introduced legislation banning the export of unprocessed tanzanite to India (like many gemstones, most tanzanite is cut in Jaipur). The ban has been rationalized as an attempt to spur development of local processing facilities, thereby boosting the economy and recouping profits. This ban will be phased in over the next two years, until which time only stones over 0.5 grams are affected.
This is a grave situation for the city of Jaipur, as one-third of its annual gem exports are of tanzanite. Some members of the industry fear the ban will set a dangerous precedent, leading Tanzania to ban the export of all raw gem material, including the country's production of tsavorite, diamond and ruby.
The mineral diamond is a crystalline form, or allotrope, of carbon (other allotropes of carbon include graphite and fullerene). It is one of the most known and most useful of more than 3,000 known minerals. Diamonds are renowned for their superlative physical qualities, especially their hardness—the word "diamond" derives from the ancient Greek adamas (αδάμας; "impossible to tame")—and their high dispersion of light. These properties and others make diamond valued for use in jewelry and a variety of industrial applications. Most diamonds are mined from volcanic pipes, where they have been deposited by deep-origin volcanoes drawing material from over 90 miles (150 km) deep within the Earth, where the pressure and temperature is suitable for diamond formation. Most diamonds are mined in central and southern Africa, although significant deposits have also been discovered in Canada, Russia, Brazil, and Australia. About 130 million carats (26,000 kg) of diamonds are mined annually, with a total value of nearly $9 billion. In addition, nearly four times that mass is artificially produced as synthetic diamond.
The gemological appeal of diamonds lies in their hardness and optical properties. Diamonds used as gems are cut and polished into a number of faceted shapes in order to accentuate these attractive qualities. The hardness of diamonds allows them to hold a polish extremely well and resist scratching (only other diamonds can scratch a diamond), giving excellent luster. The dispersion of white light into a rainbow of colors, known in the trade as fire, is the other primary characteristic of gem diamonds, and has been highly prized throughout history. Gem diamonds are commonly judged by the four Cs: carat, clarity, color, and cut. Diamonds have been treasured as gems since at least 2,500 years ago, when they were used in religious icons in India. Popularity of diamonds as gemstones increased starting in the 19th century as new cutting designs that display diamonds' gem qualities better were developed.
Industrial use of diamonds has historically been associated with their hardness; this property makes diamond the ideal material for cutting and grinding tools — common applications include the cutting surfaces of saw blades and drill bits, or use of diamond powder as an abrasive. Other specialized applications also exist or are being developed, including use as semiconductors: some blue diamonds are natural semiconductors, in contrast to most other diamonds, which are excellent electrical insulators. Industrial-grade diamonds are either unsuitable for use as gems or synthetically produced, which lowers their price and makes their use economically feasible. Industrial applications, especially as drill bits and engraving tools, also date to ancient times.
The production and distribution of diamonds is largely consolidated in the hands of a few key players, and concentrated in traditional diamond trading centers (the most important being Antwerp). The De Beers Group, based in Johannesburg, South Africa and London, England, has been the largest player in the diamond industry for over one hundred years; the company and its subsidiaries own mines that produce some 40 percent of annual world diamond production, and control distribution channels handling nearly two thirds of all gem diamonds. Some controversy over diamonds has been generated because of the monopolistic practices historically employed by De Beers including strict control of supply and alleged price manipulation, as well as the practice by some African revolutionary groups of selling conflict diamonds in order to fund their often violent activities.
Diamond is a transparent crystal of pure carbon consisting of tetrahedrally bonded carbon atoms. Humans have been able to adapt diamonds for many uses because of the material's exceptional physical characteristics. Most notable among these properties are the extreme hardness of diamond and its high dispersion index. These two properties form the basis for most modern applications of diamond.
Crystal structure: Diamonds typically crystallize in the cubic crystal system and consist of tetrahedrally bonded carbon atoms. Lonsdaleite is a polymorph of diamond (and a distinct mineral species) that crystallizes with hexagonal symmetry; it is rarely found in nature, but is characteristic of synthetic diamonds. A cryptocrystalline variety of diamond is called carbonado. A colorless, grey or black diamond with a tiny radial structure is a spherulite.
The tetrahedral arrangement of atoms in a diamond crystal is the source of many of diamond's properties; graphite, another allotrope of carbon, has a rhombohedral crystal structure and as a result shows dramatically different physical characteristics — contrary to diamond, graphite is a very soft, dark grey opaque mineral.
Hardness: Diamond is the hardest known naturally occurring material, scoring 10 on the relative Mohs scale of mineral hardness and having an absolute hardness value of between 167 and 231 gigapascals in various tests. Diamond's hardness has been known since antiquity, and is the source of its name. However, aggregated diamond nanorods, an allotrope of carbon first synthesised in 2005, are now believed to be even harder than diamond.
Broad industrial applications of diamond are based on the extraordinary hardness of diamond. As the hardest known naturally occurring material, diamond can be used to polish, cut, or wear away any material, including other diamonds. Common industrial adaptations of this ability include diamond-tipped drill bits and saws.
The hardness of diamonds also contributes to its suitability as a gemstone. Because it can only be scratched by other diamonds, it maintains its polish extremely well, keeping its luster over long periods of time. Unlike many other gems, it is well-suited to daily wear due to its resistance to scratching — perhaps contributing to its popularity as the preferred gem in an engagement ring or wedding ring, which are often worn every day.
Toughness: Unlike hardness, which only denotes resistance to scratching, diamond's toughness is only fair to good. Toughness relates to a material's ability to resist breakage from forceful impact. As with any material, the macroscopic geometry of a diamond contributes to its resistance to breakage. Diamonds cut into certain particular shapes are therefore more prone to breakage than others.
Color: Diamonds occur in a variety of transparent hues — colorless, white, steel, blue, yellow, orange, red, green, pink, brown — or colored black. Diamonds with a detectable hue to them are known as colored diamonds. Colored diamonds contain impurities or structural defects that cause the coloration, while pure or nearly pure diamonds are transparent and colorless. Most diamond impurities replace a carbon atom in the crystal lattice. The most common impurity, nitrogen, causes a yellowish or brownish tinge.
Thermodynamic stability: At surface air pressure (one atmosphere), diamonds are not as stable as graphite, and so the decay of diamond is thermodynamically favorable (ΔG = −2.99 kJ / mol). Diamonds will burn at approximately 800 degrees Celsius, providing that enough oxygen is available. This was shown in the late 18th century, and previously described during Roman times. So, despite the popular advertising slogan, diamonds are not forever. However, owing to a very large kinetic energy barrier, diamonds are metastable; under normal conditions, it would take an extremely long time (possibly more than the age of the Universe) for diamond to decay into graphite.
Sterling silver is an alloy of silver containing 92.5% pure silver and 7.5% other metals, usually copper. The millesimal fineness is 925. Sterling silver objects are usually stamped with either the word "Sterling" or ".925", or the Lion Passant mark as part of the Hallmark.
Fine silver (99.9% pure) is generally too soft for producing large functional objects, and in Sterling the silver is usually alloyed with copper to give strength whilst preserving the ductility of the silver and a high precious metal content. Other metals can replace the copper, a recent development being the use of germanium to reduce firescale in manufacturing and to give a high resistance to tarnish.
The term "Sterling Silver", in reference to the .925 grade of silver, emerged in England by the 13th century.
The terms "sterling" and "pound sterling", seem to have acquired their meaning over a period of time, and from several convergent sources. The first mention is that of "sterilensis" in 1078, and by the thirteenth century (by the 1200's) the term sterling had appeared.
It seems quite possible that Sterling Silver may have been known first as "Easterling Silver". The term "Easterling Silver" was used to refer to the grade of silver that had originally been used as the local currency in an area of Germany, known as "The Easterling".
This "Easterling" consisted of five towns in the eastern part of Germany which banded together in the 12th century under the name of the Hanseatic League. The Hanseatic League proceeded to engage in considerable commerce with England. In payment for English cattle and grain, the League used their local currency. This currency was in the form of 92.5% silver coins. England soon learned that these coins, which they referred to as "the coins of the Easterlings", were of a reliably high quality and hardness.
King Henry II set about to adopt the alloy as the standard for English currency. He imported metal refiners from the Easterling and put them to work making silver coins for England. The silver these refiners produced came into usage as currency by 1158 in the form of what are now known as "Tealby Pennies", and was eventually adopted as a standard alloy throughout England. The original term of "Easterling Silver" was later abbreviated to "Sterling Silver".
Though the coin weights and silver purity changed considerably in the intervening time (reaching a low point before the reign of Elizabeth I, who reinstated Sterling Silver coinage for the first time since the early 14th century), the pound sterling was used as currency in England from the 12th century until the middle of the 20th century. Specifically this was in the silver coins of the British Empire -- Britain, British colonies and some former British colonies. This sterling coin silver is not to be confused with the Coin silver standard.
Sterling silver, while no longer used in circulating currency anywhere in the world, is still used for flatware, jewellery and plate, and is a grade of silver respected for both relatively high purity and sufficient hardness to form durable objects in daily use.
Another credible theory is that, since mint marks on Sterling Silver pennies have included a star and a starling, this may be the origin of the word -- as a simple corruption of, for example, "starling silver" with common reference to the circulating coin
Fine silver is 99.9% silver or better. This grade of silver is used to make bullion bars for international commodities trading. In the modern world Fine Silver is understood to be too soft for general use.
Britannia silver is purer than sterling, at least 95.84% silver and up to 4.16% copper. Its marks were Britannia and a lion's head in profile.
The Britannia standard was a standard of plate obligatory in Britain between 1697 and 1720 to try to help prevent British sterling silver coins from being melted to make plate. It became an optional standard thereafter, and in the United Kingdom and Ireland is now denoted by the millesimal fineness hallmark "958", with the symbol of Britannia being applied optionally.
Mexican silver is also purer than sterling, usually 95% Silver and 5% Copper. Mexico is the only country currently using silver in its circulating coinage, but these coins are not minted from 95% "Mexican" Silver.
Coin silver is 90% silver and 10% copper as dictated by United States FTC guidelines.
Coin Silver is lower grade than sterling. The Coin Silver standard was established in the US in the 1820s. This grade of silver was used in the silver coinage of the US as well as other countries that used silver currency minted in the US, such as Panama and the Philippines.
For industrial uses, for example in electronics, alloys such as CuAg are favoured, which contains 72% silver and 28% copper and is known for its thermal conductivity.
As the purity of the silver increases, the problem of corrosion or tarnishing lessens.
Chemically, silver is not very active — it does not react with oxygen or water at ordinary temperatures, so does not easily form a silver oxide. However, the other metal in the alloy, usually copper, may react with oxygen in the air.
However, silver is highly reactive toward sulfur. Silver tarnish is the formation of black silver sulfide on the surface of the metal, and is caused by sulfur and sulfides which attack the surface of the silver. Because of this, the rate of discolouration of silver by tarnish is worse with higher levels of these airborne pollutants.
Eggs, which contain a considerable quantity of sulfur as a constituent of protein, tarnish silver extremely quickly. Small amounts of sulfide occur in the atmosphere naturally, but another major man-made source is hydrogen sulfide (H2S), which is added to natural gas used domestically. Hence a gas flame can also tarnish silver.
The black silver sulfide (Ag2S) is among the most insoluble salts in aqueous solution, a property that is exploited for separating silver ions from other positive ions.
A very popular technique for removing tarnish involves the creation of an electrochemical cell. If the other metal is anodic relative to silver, then the silver in the sulfide will revert to metallic silver. The metal at the anode will be oxidized. The sulfide ions can travel to the anode via the electrolyte (solution). Metals that will work are iron, zinc, aluminium and magnesium. Aluminium foil is cheap.
A typical procedure is to line a pyrex glass dish with alumimium foil so the bright side of the foil will contact the solution. Add one litre of water, and heat until near boiling.
Add one tablespoon of sodium chloride and one tablespoon of sodium bicarbonate, and gently stir to dissolve. Ensure that the silverware has been washed in warm dishwashing detergents, and well rinsed in warm water to remove dirt and grease.
Carefully add the silverware to the dish, ensuring that each item is in contact with the aluminium foil, and boil until the tarnish has disappeared, turning the silverware if necessary. The continuous boiling is required so that the aluminium oxide continually exposes the unreacted aluminium surface beneath, otherwise the reaction will not occur. The aluminium will gradually be converted to aluminium oxide. The hydrogen that is generated in the reaction will combine with the sulfide ions to produce some hydrogen sulfide gas (rotten egg gas).
It should be noted that the process is not converting the silver back to the original hard, lustrous surface, but into a soft, white powder that can be removed easily by rubbing with a little bicarbonate of soda paste. The silver powder will be easier to remove than the tarnish would have been.
A gemstone is a mineral, rock (as in lapis lazuli) or petrified material that when cut or faceted and polished is collectible or can be used in jewellery. Others are organic, such as amber (fossilised tree resin) and jet (a form of coal). Some beautiful gemstones are too soft or too fragile to be used in jewelry, for example, single-crystal rhodochrosite, but are exhibited in museums and are sought by collectors of mineral or crystal specimens.
Gemstones are described and differentiated by gemmologists by certain technical specifications. First, what is it made of, its chemical composition. Diamonds for example are made of carbon (C), rubies of aluminium oxide (Al2O3). Next, many gems are crystals which are classified by crystal system such as cubic or trigonal or monoclinic. Another term used is habit, the form the gem is usually found in, for example diamonds which have a cubic crystal system are often found as octahedrons.
Gems are classified into different groups, species and varieties. For example, ruby is the red variety of the species corundum that belongs to the spinel or hematite group. Emerald (green), aquamarine (blue), bixbite (red), goshenite (colorless), heliodor (yellow), and morganite (pink) are all varieties of the mineral species beryl.
Gems have a certain refractive index, a certain dispersion, a certain specific gravity, a certain hardness, a certain cleavage, a certain fracture, a certain luster. They may exhibit pleochroism of a sort, or double refraction to a degree and have an optic sign. They may have a certain luminescence and a distinctive absorption spectrum.
Certain material or flaws within a stone may be present as characteristic inclusions. And the gem may occur in certain locations, "occurrence." Gems from different locations may display different characteristics which may aid in identification.
A gemstone is prized especially for great beauty or perfection. Hence, appearance is almost the most important attribute of gemstones. Characteristics that make a stone beautiful or desirable are colour, unusual optical phenomena within the stone, an interesting inclusion such as a fossil, rarity, and sometimes the form of the natural crystal. In terms of beauty, it is unsurprising that diamond is prized highly as a gemstone, since it is the hardest substance known and is able to reflect light with fire and sparkle when faceted. However, it is important to understand that diamonds are far from rare with millions of carats mined each year.
Traditionally, common gemstones were classified into precious stones (cardinal gems) and semi-precious stones. The former category was largely determined by a history of ecclesiastical, devotional or ceremonial use and rarity imposed by the limits of known deposits and available collection methods. Only five types of gemstones were considered precious: diamond, ruby, sapphire, emerald, and amethyst. In current usage by gemmologists, all gems are considered precious, although four of the five original "cardinal gems" are usually—but not always—the most valuable.
Another category of gemstones which is still in use is that of 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. Here are included andalusite, axinite, cassiterite, clinohumite, iolite, among others all of which are durable, rare, and in better examples quite attractive.
The factors influencing the esteem in which gems are held are few in number but extremely important because they so directly affect value. These are attractiveness, durability, rarity, fashion, and size. They are not fixed in scope by any means and the predominance of one factor may compensate for shortcomings in another.
Some gemstones are manufactured to imitate other gemstones. For example, cubic zirconia is a synthetic diamond simulant composed of zirconium oxide. The imitations copy the look and colour of the real stone but possess neither their chemical nor physical characteristics. However, true synthetic gemstones are not necessarily imitation. For example, diamond, ruby, sapphire and emerald have been manufactured in labs, which possess very nearly identical chemical and physical characteristics as the genuine article. Synthetic corundums, including ruby and sapphire, are very common and they cost only a fraction of the natural stones. Smaller synthetic diamonds have been manufactured in large quantities as industrial abrasives for many years. Only recently, larger synthetic diamonds of gemstone quality, especially of the coloured variety, have been manufactured.
There are over 130 species of minerals that have been cut into gems with 50 species in common use. These include:
Alexandrite and other varieties of chrysoberyl
Amethyst (originally a "cardinal gem", but now no longer so, since huge quantities were discovered in Brazil and the price plummeted)
Aquamarine and other varieties of beryl
Olivine (Peridot)
Opal (Girasol)
Quartz and its varieties, such as tiger's-eye, citrine, agate, and amethyst
Minerals that infrequently occur in gem quality form:
Andalusite
Axinite
Cassiterite
Iloite
Kornerupine
Artificial or synthetic materials used as gems include:
High-lead glass
Synthetic cubic zirconia
Synthetic corundum
Synthetic spinel
Synthetic moissanite
There are a number of organic materials used as gems, including:
This article is licensed under the "GNU Free Documentation License". It uses material from the Wikipedia articles "Jewelry", "Tanzanite", "Diamonds", "Sterling Silver" and "Gemstones".
