Rock (geology)
In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter.
The study of rocks involves multiple subdisciplines of geology, including petrology and mineralogy.
Mining developed to extract rocks from the Earth and obtain the minerals within them, including metals.
Modern technology has allowed the development of new human-made rocks and rock-like substances, such as concrete.
Plutonism was developed as a theory during this time, and the discovery of radioactive decay in 1896 allowed for the radiocarbon dating of rocks.
[2] Rocks are composed primarily of grains of minerals, which are crystalline solids formed from atoms chemically bonded into an orderly structure.
[4]: 3 Some rocks also contain mineraloids, which are rigid, mineral-like substances, such as volcanic glass,[5]: 55, 79 that lack crystalline structure.
[6] The proportion of silica in rocks and minerals is a major factor in determining their names and properties.
By increase or decrease in the proportions of their minerals, they pass through gradations from one to the other; the distinctive structures of one kind of rock may thus be traced, gradually merging into those of another.
Hence the definitions adopted in rock names simply correspond to selected points in a continuously graduated series.
This magma may be derived from partial melts of pre-existing rocks in either a planet's mantle or crust.
Typically, the melting of rocks is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition.
This process causes clastic sediments (pieces of rock) or organic particles (detritus) to settle and accumulate or for minerals to chemically precipitate (evaporite) from a solution.
[5] About 7.9% of the crust by volume is composed of sedimentary rocks, with 82% of those being shales, while the remainder consists of 6% limestone and 12% sandstone and arkoses.
An intrusion of magma that heats the surrounding rock causes contact metamorphism—a temperature-dominated transformation.
Familiar examples of non-foliated metamorphic rocks include marble, soapstone, and serpentine.
In the Solar System, Mars, Venus, and Mercury are composed of rock, as are many natural satellites, asteroids, and meteoroids.
[34] Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam.
Mining is required to obtain any material that cannot be grown through agricultural processes, or created artificially in a laboratory or factory.
Mining in a wider sense comprises extraction of any resource (e.g. petroleum, natural gas, salt or even water) from the earth.
These potential impacts have led to most of the world's nations adopting regulations to manage negative effects of mining operations.
[39] Early Stone Age tools were simple implements, such as hammerstones and sharp flakes.
