Silver is the metallic element with the atomic number 47. Its symbol is Ag, from the Latin argentum, derived from the Greek ὰργὀς (literally "shiny" or "white"), and ultimately from a Proto-Indo-European language root reconstructed as *h₂erǵ-, "grey" or "shining". 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.