Gold:
Gold is a natural forming metal in which its natural state offers an unequalled stability and beauty. Moreover, its malleability permits to manufacture of almost transparently thin leaves, while from one ounce of gold it is possible to draw a fine wire of fifty miles long. The ductility of gold diminishes in relation to the amount of other metals alloyed with it. Its melting point is between 1832 and 1940 F; it is not subject t o normal oxidization and is insoluble in nearly all common acids. The density of gold is about 19.3 times the weight of an equal volume of water and about 3 times of an Iron in the same size.
Although present in very short measure in almost all rocks, in the sea and rivers, in sand and even inplants, the areas which are rich in gold are few and scattered throughout the world. Mainly it comes from the deepest recesses of the earth and is probably the first known to man. Layers of gold are easy to reach near the earth’s surface. By mining process it will come out from earth. Raw gold is known as ‘Nugget’, & the gold found from river beds called ‘Alluvial’.
Gold was first found in India (when it’s called Hindustan), before millions of years ago. There is no proper history available for the mining of gold, but before more than 10000 million years ago the Indians were familiar with gold. The Indians introduced the entire world about the art of jewellery, metals & metal working. As the world history first use of gold had been traced back to 4000 years B.C. The Egyptians and Romans are developed gold fever, u sing it for coins & jewellery ornamentation. No more earliest history of any culture, that says they knew about gold before more than 4000 years. But as Indian history before millions of years ago Indians were had gold coins (called Suvarna Mudrica or Sona-Mohar), exclusive gold jewelleries and gold utensils.
Pure gold is too soft for practical uses, but as an alloy with base metals for used in jewellery. Silver, copper or other metals are usually main base metals for alloying for ordinary purposes as jewellery or coins. Gold is basically yellow (golden) coloured metal, but when alloyed with different metals it appears different colours like whitish (called White Gold), greenish (Green Gold), reddish (Red Gold), bluish (Blue Gold), pinkish (Pink Gold). Purity of Gold is known as “Karat”. 100% pure Gold is called 24 karat fine or 100 touch Gold. After alloying with other metals, gold purity will decreases to 22, 18, 16, 14 karat etc… Gold above 18 karat is used for special work like only Gold Jewellery, Kundan Jewellery, Thewa Jewellery, Statues etc…, other purities used for diamonds & gem-stones studded Jewellery. Gold is used in International market as a currency too.
Gold is also used for medicine as a best health tonic, in food & drinks, other industries & electronic field. Because of it is a inert metal also used for covering costly parts of machinery & satellites. 
Silver: || TOP ||
Silver is widely diffused but it rarely found in the native state. It is originally as widespread as Gold or combined with sulphur, arsenic, antimony or chlorine in ores such as argentite (Ag2S), horn silver (AgCl), and pyrargyrite (Ag3SbS3). The principal sources of silver are the ores of copper, copper-nickel, lead, and lead-zinc occurring in nearly all the volcanic rocks. Whereas, Gold remains unaltered by the action of the elements and is often carried long distance from its place of origin Silver on the contrary is only to be found in the rocks where it is originated.
The history of silver is as same as gold history. The first known country is India (Hindustan). Before millions of year ago Indians used silver as a wearing purpose (as an ornaments), as an utensils, as a medicine, as
weapons and also used in cloths as a thread.
Pure Silver has a brilliant white colour & is the whitest of all metals. None surpasses it in luster and in hardness it ranges between pure Gold & pure Copper. It is more fusible than Copper & Gold, melting at a bright heat or at 1761 F. It is commonly use for the purpose of alloying Gold in its pure state, but if too much be added it makes the Gold pale.
It is almost as plastic as pure Gold and is too soft to make durable objects that require lightness and stability of form. This defect is overcome by alloying it with a little Copper. An alloy of 925 parts fine Silver & 75 parts Copper is called 925-1000 fine or what is commonly known as sterling Silver. This alloy is used almost universally for jewellery & the best silverware.
The word “Sterling” is the quality mark for the best in Silver. The origin of the term dated back to the 12th century when give free towns banded together in the eastern part of Germany calling themselves the Hanseatic League. They were free to make their own laws and issue their own currency. When trading with British merchants, they paid for the British products with Silver coins. These coins attracted the attention of the Britishers for their consistency of metal & dependability of weights and were, there for referred to as the coins of the Ester lings. In due time after the British adopted the characteristic of these Coins, the metal and the coin became known as fineness & Quality.
Platinum: || TOP ||
Platinum is an extremely rare metal, occurring as only 0.003 ppb (Parts-per notation) in the earth’s crust, and is 30 times rarer than gold. It is sometimes mistaken for silver (Ag) but platinum is whiter in appearance. Platinum is often found chemically uncombined as native platinum and alloyed with iridum as platiniridium.  Most often the native platinum is found in secondary deposits, and it is combined with the other platinum group metals in alluvial deposits. Platinum together with the rest of the platinum metals is obtained commercially as a by-product from nickel and copper mining and processing. During electro refining of copper, noble metals such as silver, gold and the platinum group metals as well as selenium and tellurium settle to the bottom of the cell as anode mud, which forms the starting point for the extraction of the platinum group metals.
Platinum occurs naturally in the alluvial sands of various rivers, though there is little evidence of its use by ancient peoples. However, the metal was used by pre-Columbian Americans near modern-day Esmeraldas, Ecuador to produce artifacts of a white gold-platinum alloy. The first European reference to platinum appears in 1557 in the writings of the Italian humanist Julius Caesar Scaliger as a description of an unknown noble metal found between Darien and Mexico,
Platinum is an extremely much harder than gold. As a pure metal, platinum is silvery-white in appearance, lustrous, ductile, and malleable. It does not oxidize at any temperature, though it is corroded by halogens, cyanides, sulphur, and caustic alkalis. Platinum is insoluble in hydrochliric and nitric acid, though it does dissolve in aqua regia to form chloroplatinic acid, H2PtCl6.
Platinum's wear- and tarnish-resistance characteristics are well suited for making fine jewellery. Platinum is more precious than gold and silver. Platinum, like other industrial commodities, is more volatile than gold.
During periods of sustained economic stability and growth, the price of platinum tends to be as much as twice the price of gold, whereas, during periods of economic uncertainty, the price of platinum tends to decrease due to reduced industrial demand, falling below the price of gold. Gold prices are more stable in slow economic times because gold is considered a safe haven and gold demand is not driven by industrial uses. In the 18th century, platinum's rarity made King Louis XV of France declare it the only metal fit for a king. Platinum possesses high resistance to chemical attack, excellent high-temperature characteristics, and stable electrical properties. All these properties have been exploited for industrial applications.
The metal is extensively used in jewellery, wire, and vessels for laboratory use, and in many valuable instruments. It is also used for electrical contacts, corrosion-resistant apparatus, and in dentistry.
Palladium: || TOP ||
Palladium is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it palladium after the asteroid Pallas, which was turn, was named after the epithet of the Greek goddess Athena, acquired by her when she slew Pallas. The symbol for palladium is Pd, and its atomic number is 46.
Palladium is found with platinum and other metals of the platinum group in placer deposits of Russia, South America, North America, Ethiopia, and Australia. It is also found associated with the nickel-copper deposits of South Africa and Ontario. Palladium's separation from the platinum metals depends upon the type of ore in which it is found.
The unique properties of palladium and other platinum group metals account for their widespread use. One in four goods manufactured today either contain platinum group metals or play a key role during their manufacturing process. Over half of the supply of palladium and its sister metal platinum goes into catalytic converters, which convert up to 90% of harmful gases from auto exhaust into less harmful substances. Palladium’s precious metal qualities and appearance generate significant consumption in the luxury jewellery market.
Palladium itself has been used as a precious metal in jewellery since 1939, as an alternative to platinum or white gold. This is due to its naturally white properties, giving it no need for rhodium plating. It is slightly whiter, much lighter and about 12% harder than platinum. Similar to gold, palladium can be beaten into a thin leaf form as thin as 100 nm (1/250,000 in).
Rhodium: || TOP ||
Rhodium is a chemical element that is a rare, silvery-white, hard transition metal and a member of the platinum group. Rhodium is found in platinum ores and is used in alloys with platinum and as a catalyst. It is abbreviated in the periodic table to Rh and has atomic number 45.
It is typically the most expensive precious metal approx 10 time costly metal than gold. It is not a feasible material to make solid jewellery because it is too stressed and brittle, but rhodium is fabulous as a plating for jewellery because it is glitteringly, dazzlingly, white and mirror-like. It makes diamonds look bigger and better because it's so bright that it's almost hard to see where the stones end and the metal begins. Nothing sets off diamonds like rhodium plating does, but it is only a plating and therefore it will wear off and require replating Rhodium plating is a finish that is applied to all white gold platinum and also for yellow gold jewellery to give it a white look. It will look exactly the same on the low cost and most expensive of jewellery, as you are seeing the reflective brilliance brilliant white colour of the rhodium plating but not the true colour of the metal below. In time the rhodium plating will wear off and the true colour of the metal will visible.
Copper: || TOP ||
Copper, as native copper, is one of the few metals to naturally occur as an un-compounded mineral. Copper was known to some of the oldest civilizations on record, and has a history of India the use that is similer to gold and silver, before millioms of years old.
As the world history about 11,000 years old. No one knows exactly when copper was first discovered, but earliest estimates place this event around 9000 BC in the Middle East. A copper pendant was found in what is now northern Iraq that dates to 8700 BC. It is probable that gold and iron were the only metals used by humans before copper. By 5000 BC, there are signs of copper smelting: the refining of copper from simple copper compounds such as malachite or azurite.
Alloying to make brass or bronze was realized soon after the discovery of copper itself. There exist copper and bronze artifacts from sumerian cities that date to 3000 BC, and Egyption artifacts of copper and copper-tin alloys nearly as old. In one pyramid, a copper plumbing system was found that is 5000 years old. The Egyptians found that adding a small amount of tin made the metal easier to cast, so copper-tin (Bronze) alloys were found in Egypt almost as soon as copper was found to the world as world history.
Throughout history, copper's use in art has extended far beyond currency.Upto 18th century A.D., thin sheets of copper were commonly used as a canvas for paintings. Silver plated copper was used in the pre-photograph The Statue of Liberty, dedicated on October 28, 1886, was constructed of copper thought to have come from French-owned mines in Norway.Today copper used for alloying to gold, for jewellery, for industrial purpose, for electronic and many more uses.
Nickel: || TOP ||
Nickel is a silvery-white lustrous metal with a slight golden tinge that takes a high polish. It is one of the four magnetic elements that are magnetic at room temperature. It belongs to the transition metals and is hard and ductile. Its use has been traced as far back as 3500 BC, but it was first isolated and classified as a chemical element in 1751 byAxel Fredrik Cronstedt, who initially mistook its ore for a copper mineral. Its most important ore minerals are laterites, including limonite, garnierite and pentlandite. Major production sites include Sudbury in Canada and in Russia. The metal is corrosion-resistant, finding many uses in alloys, as a plating, in the manufacture of coins, magnets and common household utensils, as a catalyst for hydrogenation, and in a variety of other applications. Enzymes of certain life-forms contain nickel as an active center making the metal essential for them.
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