Silver is one of the most famous precious metal s, and has been used for ornamental purposes since the earliest of times. Most silver is extracted from silver ore s, but considerable amounts are mined from Native Silver. Silver can be found pure, but is usually mixed with small amounts of gold, arsenic, and antimony. A natural alloy of gold and silver is known as Electrum, and is usually classified as a variety of Gold. Silver is a very resistant mineral. It does not dissolve in most solvent s, and won't react to oxygen or water. However, it has a detrimental reaction to sulfur and sulfides, which causes it to tarnish on exposed surfaces.