Silver
Silver is a chemical element with symbol Ag (from the Latin "", derived from the Proto-Indo-European "h₂erǵ": "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. The metal is found in the Earth's crust in the pure, free elemental form ("native silver"), as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. Most silver is produced as a byproduct of copper, gold, lead, and zinc refining.
Philadelphia Gold and Silver Index
The Philadelphia Gold and Silver Index is an index of thirty precious metal mining companies that is traded on the Philadelphia Stock Exchange. The index is represented by the symbol "XAU", which may be a source of some confusion as this symbol is also used under the ISO 4217 currency standard to denote one troy ounce of gold. The Philadelphia Gold and Silver Index and the NYSE Arca Gold BUGS Index are the two most watched gold indices on the market.