Silver is the 68th most abundant element in the Earth's crust and 65th in cosmic abundance. It is found in small quantities in many locations on Earth. Large amounts of the metal have been mined in both North and South America, which together produce over half the world total. Its mostly important ores are sulfides, of which argentite (silver sulfide, Ag2S) is the most common. Silver often occurs as a minor constituent in the ores of copper, lead, and zinc. Refinement of these metals yields large quantities of silver (and some gold). Silver is found in minute quantities in seawater.
The atomic weight of silver is 107.868, and natural silver consists of two stable isotopes: silver-107 (51.82%) and silver-109 (48.18%). The melting point of the metal is 960.8 deg. C and it boils at 2,210 deg. C. Next to gold, silver is the most malleable and ductile metal known. It is harder than gold but softer than copper. This softness limits its use, even for coinage, unless it is alloyed with about 10% copper. When alloyed with 7.5% copper, it is known as sterling silver. As a pure element it can absorb oxygen in the amount of 20 times its own volume at its melting point. It is the best conductor of heat and electricity of any of the metals.
Although silver dissolves readily in nitric acid, it resists such acids as hydrochloric, sulfuric, acetic, citric, lactic, phosphoric, oxalic, and benzoic. It will also dissolve in solutions of sodium or potassium cyanide, but not in sodium or potassium hydroxide solutions or fused salts. It does not normally oxidize in air, but it does react with sulfides and with the hydrogen sulfide found in the atmosphere of many industrial cities, forming a black film of silver sulfide. Major producers of silver in order of their production are Mexico, Peru, the USSR, Canada, Australia, and the United States.