What sterling silver is
Silver is somewhat rare and expensive, although not as expensive as gold. Slag dumps in Asia Minor and on islands in the Aegean Sea indicate that man learned to separate silver from lead as early as 3000 B.C. Pure silver has a brilliant white metallic lustre. It is a little harder than gold and is very ductile and malleable. Pure silver has the highest electrical and thermal conductivity of all metals, and possesses the lowest contact resistance. Silver iodide, AgI, is (or was?) used for causing clouds to produce rain.
Sterling Silver is 92.5% silver and 7.5% copper. 99.9% silver is called "Fine silver." Sterling components and jewelry made in the USA are often stamped "Sterling." Goods made for international trade are often marked "925" indicating the 92.5% fineness. "Coin" silver is used in some countries and could be marked "900" or "800" depending on fineness.