Silver has been known and used for thousands of years and it is considered as one of the three precious metals along with gold and platinum. Pure silver is very soft metal with its lustrous white color. Although it is harder than gold and much more plentiful, but still too soft in its natural state and required to be mixed with a harder metal for the use in jewelry manufacturing. It ranks second in ductility and malleability to gold. It is normally stable in pure air and water but tarnishes when exposed to ozone, hydrogen sulfide or sulfur.
Silver is the brightest reflector of any metal (except for liquid mercury) and can be polished to a high sheen that even platinum can't achieve. It has also the highest electrical and thermal conductivity of all metals, even higher than copper. Most silver is produced as a by-product of copper, gold, lead, and zinc mining. Commercial grade fine silver is at least 99.9% pure silver and purities greater than 99.999% are available. Mexico is the world's largest silver producer which contributed 15% of the annual production of the world. Canada, Peru, Australia and the United States are the other major countries, which are producing silver.
It has long been valued as a precious metal and used in currency, jewelry, ornaments, and utensils. Now-a-days, silver is also used in photographic film, electrical contacts, mirrors, dentistry and surgical implants.
Purity of silver is based on the other metals, which are available in the silver in the form of metal alloys. Unlike gold, but like platinum, silver purities are expressed as units of a 1,000 parts. On the basis of its purity, it can be described as below:
Pure / Fine Silver
It is the purest form of silver with 99.9% purity. It is also known as fine silver. In this form, silver is too soft to use for jewelry. Purity - 999 points (99.9% pure silver)
Due to the softness of pure / fine silver, it can not be used in its purest form for jewelry. Therefore, to give strength and durability to the pure silver, it is alloyed with other harder metals, usually copper. A mixture of 92.5% of pure silver and 7.5% of copper is known as Sterling Silver. Sterling Silver is one of the most familiar and used form of silver alloys. Purity - 925 points (92.5% pure silver)