is the extraction of valuable minerals
or other geological
materials from the earth, usually from an ore
) seam. Any material that cannot be grown and harvested through agricultural
processes (such as farming
), or created artificially
in a laboratory
, is usually mined. Materials recovered by mining include metals
, ranging from base metals
(such as iron
) to precious metals
(such as gold and silver) to uranium
, as well as coal
, oil shale
, rock salt
. Mining in a wider sense comprises extraction of any non-renewable resource
, natural gas
, or even water
Mining has long been an essential part of human civilization and technology. In the Neolithic Stone Age, Bronze Age, and Iron Age, mining provided the stone, copper and tin to make the bronze, and the iron. Discoveries of valuable minerals have sparked gold and silver rushes, leading to the mass migration of many thousands of individuals to places around the world. With the invention of the steam engine, coal mining became critical to fueling the Industrial Revolution. Newer technologies such as nuclear power and consumer electronics have increased demands for previously unimportant minerals, leading to new cycles of mineral discovery and mining.
is a chemical element
in the carbon group
with symbol Pb
) and atomic number
82. Lead is a soft and malleable metal
, which is regarded as a heavy metal
and poor metal
. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes
to a dull grayish color when exposed to air. Lead has a shiny chrome-silver luster when it is melted into a liquid.
Lead is used in building construction, lead-acid batteries, bullets and shot, weights, as part of solders, pewters, fusible alloys, and as a radiation shield. Lead has the highest atomic number of all of the stable elements, although the next higher element, bismuth, has a half-life that is so long (much longer than the age of the universe) that it can be considered stable. Lead, at certain contact degrees, is a poisonous substance to animals, including humans. It damages the nervous system and causes brain disorders.
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