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.
Proustite
Proustite is a sulfosalt mineral consisting of silver sulfarsenide, AgAsS, known also as light red silver or ruby silver ore, and an important source of the metal. It is closely allied to the corresponding sulfantimonide, pyrargyrite, from which it was distinguished by the chemical analyses of Joseph L. Proust (1754–1826) in 1804, after whom the mineral received its name.