Pure silver is a chemical element, but nearly all silver encountered in daily life is a metal alloy. Silver (Ag) is a naturally occurring pure substance with a highly lustrous, white color. Its properties in elemental form make it impractical for most applications, necessitating mixing it with other metals to create a more usable material. This process transforms the pure element into a substance with superior mechanical properties, which is the definition of an alloy.
Elemental Silver and the Definition of an Alloy
Elemental silver exists as a pure metal, possessing the highest electrical and thermal conductivity of any known metal. This pure form is referred to as fine silver and is typically 99.9% pure, with the remaining 0.1% consisting of trace elements.
A metal alloy is a homogeneous mixture of two or more elements, where at least one is a metal. Alloys are created by melting the constituent elements together, allowing them to dissolve and solidify. This mixing produces a material with characteristics that are improved over those of the pure base metal. The addition of a second element alters the crystalline structure, enhancing properties like hardness or resistance to wear.
Why Pure Silver is Unsuitable for Daily Use
The primary challenge with using fine silver is its extreme softness, making it highly susceptible to damage during regular handling. Pure silver ranks only 2.5 to 3 on the Mohs scale of hardness, meaning it is easily scratched, dented, or deformed. Its atomic structure allows the atoms to slide too freely past one another, resulting in high malleability and ductility but low durability for items like jewelry or flatware.
Another significant drawback is the metal’s inherent tendency to tarnish when exposed to the atmosphere. Silver readily reacts with sulfur compounds, such as hydrogen sulfide gas, which are present in the air. This reaction forms a layer of black silver sulfide on the surface, dulling its brilliant appearance. The need for increased strength and better tarnish resistance makes alloying a practical necessity for almost all commercial silver products.
Common Commercial Silver Alloys
The most common form of silver used globally is Sterling silver, an alloy that achieves a balance between purity and durability. Sterling silver is composed of 92.5% silver and 7.5% other metals, most commonly copper. This specific ratio is often stamped on items as “925,” and is one of the grades specified in international standards. The copper component significantly increases the metal’s hardness, allowing it to withstand the stresses of daily wear in jewelry, tableware, and decorative objects.
Another historical alloy is Coin silver, which typically contains 90% silver and 10% copper, often marked as “900.” This mixture was historically used for minting coins, providing a material that was harder than fine silver yet still retained high precious metal value. Fine silver, marked as “.999,” is still used, but its application is limited to items where hardness is not a concern, such as investment bullion bars and specialized electronic components.