Mining is the extraction (removal) of minerals and metals from earth. Manganese, tantalum, cassiterite, copper, tin, nickel, bauxite (aluminum ore), iron ore, gold, silver, and diamonds are just some examples of what is mined. Minerals and metals are very valuable commodities. For example, manganese is a key component of low-cost stainless steel. It is also used to de-color glass (removing greenish hues), but in higher concentrations, it actually makes lavender-colored glass. Tantalum is used in cell phones, pagers, and lap-tops. Mining in a wider sense includes extraction of any non-renewable resource such as petroleum, natural gas, or even water.Mining of stones and metal has been a human activity since pre-historic times. Modern mining processes involve prospecting for ore bodies, analysis of the profit potential of a proposed mine, extraction of the desired materials, and final reclamation of the land after the mine is closed.Mining operations usually create a negative environmental impact, both during the mining activity and after the mine has closed. Hence, most of the world's nations have passed regulations to decrease the impact. Work safety has long been a concern as well, and modern practices have significantly improved safety in mines.