Gold

No precious metal is as legendary and beautiful as Gold. Its rarity, beauty, and enigma have provided it with status as a valuable commodity throughout the history of humanity. Gold has always been used as a monetary standard, and ancient gold jewelry and ornaments dating back centuries have been found throughout the world. Gold has always been and remains the most essential jewelry component, with most precious jewelry pieces created from Gold or inlaid with a Gold setting.

Gold is the most malleable and ductile metal, which makes it very easy to work with. It never tarnishes, and is unaffected by most chemicals. However, it can discolor by exposure to chlorine, bleach, and certain detergents.

Pure Gold lacks resistance to pressure and easily bends. For this reason, Gold jewelry is always alloyed with other metals to increase its toughness and durability. The purity of Gold depends on the percentage of alloyed metal, and this number is measured in karats. The karat measurement determines the percentage of gold to other metals on a scale of 1 to 24, with 24 karats being pure gold. Common karat weights are 22 kt (91.67% gold), 18 kt (75% gold), 14 kt (58.33% gold), and 10 kt (41.67% gold). Pure 24 kt Gold is never used in jewelry as it too flexible and will be bent and mishaped even by minor touches.
 

Platinum

Platinum is the most valued precious metal; its value exceeds even that of Gold. It has a beautiful silver-white color, and, unlike Silver, does not tarnish. It is unaffected by common household chemicals and will not get damaged or discolored by chlorine, bleach, or detergents. It is tougher than all precious jewelry metals, though due to its flexible tenacity it still must be alloyed with other metals to prevent it from bending. Natural Platinum usually contains small amounts of the rare element iridium. In jewelry, iridium is alloyed with the Platinum to increase its toughness. Platinum jewelry is usually 90 to 95 percent pure.

Platinum is an extremely rare metal. This, combined with the fact that it is very resistant and doesn't tarnish, are responsible for Platinum's exorbitant value. Platinum is not an ancient metal; it wasn't until relatively modern times that Platinum was regarded as such a valuable commodity. In fact, before the 1700's, the identity of Platinum was uncertain, and Platinum was often regarded as a lesser form of Silver. The extremely high melting point of Platinum also made it difficult to melt down and fashion into jewelry. This has all changed today, with the popularity and value of Platinum soaring and its usage in jewelry very popular and exclusive.

Silver

Silver is an important precious metal, and has been used by ancient civilizations throughout history as a second to Gold in importance and value. Like Gold, it has always been used as a monetary standard, and ancient silver ornaments and silverware dating back centuries have been found throughout the world.

Silver is very malleable and ductile, and is very easy to work with. However, it is poorly resistant to pressure and easily bends. For this reason, silver is alloyed with other metals to increase its toughness and durability.

Silver jewelry, ornaments, and silverware are traditionally made from Sterling Silver. Sterling Silver is an alloy composed of 92.5% silver and the remainder 7.5% other metals, usually copper. Items made from Sterling Silver are usually engraved with the letters 925, which indicates that it is 92.5% silver.

Sterling Silver is harder and more durable than pure Silver. Sterling Silver jewelry is sometimes plated with an extremely thin layer of pure silver to provide an extra shine. Vermeil, which is used in jewelry, is Sterling Silver coated with a thin layer of Gold or occasionally Platinum. It is an inexepensive alternative to those valuable metals it is coated with.

Silver is notorious for its habit of tarnishing. Fresh Silver has a bright-metallic-white color, but almost invariably turns yellowish to blackish upon continuous exposure to air. This is caused by a chemical reaction of the silver to sulfur compounds present in the atmosphere. The only way to prevent this effect is to glaze the silver with an anti-tarnish coat. Silver should also be kept away from eggs, which are rich in sulfur. Tarnished silver can easily be restored to its original color by using tarnish-removing chemicals that are readily available. - See more at: http://www.minerals.net/gemstone/silver_gemstone.aspx#sthash.mg4D9j9e.dpuf