Fossil fuels, discussed earlier in the chapter, are the fourth class of ores, called energy minerals. When mined, ore reserves are depleted very rapidly, for they are an unrenewable resource. There are many methods by which deposits are formed, the most common of which are hydrothermal processes and crystal settling. In hydrothermal processes, veins of minerals or metals are formed when sheet-like deposits precipitated by hot water solutions that fill fractures in the earth or deposit near igneous regions. Crystal settling occurs when mineral particles in a cooling magma chamber crystallize and sink to the bottom.
Ore extraction is a complex, and often dirty process.
It is first dug up, then crushed and chemically seperated from surrounding materials. Large piles of waste rock are left and allowed to erode into water supplies, harming aquatic habitats. Mining also ruins landscapes by contributing to deforestation, air and water pollution. Such pollution endangers the lives of all populations in the environment. The growth rate of plants is slowed, causing the growth rate of the entire food chain to decrease.