Search results
Results from the WOW.Com Content Network
Also called Indianite. A mineral from the lime-rich end of the plagioclase group of minerals. Anorthites are usually silicates of calcium and aluminium occurring in some basic igneous rocks, typically those produced by the contact metamorphism of impure calcareous sediments. anticline An arched fold in which the layers usually dip away from the fold axis. Contrast syncline. aphanic Having the ...
Most rocks contain silicate minerals, compounds that include silica tetrahedra in their crystal lattice, and account for about one-third of all known mineral species and about 95% of the earth's crust. [6] The proportion of silica in rocks and minerals is a major factor in determining their names and properties. [7]
The following is a list of rock types recognized by geologists.There is no agreed number of specific types of rock. Any unique combination of chemical composition, mineralogy, grain size, texture, or other distinguishing characteristics can describe a rock type.
1. (mineral deposit) An accumulation of valuable minerals, particularly gold, formed by gravity separation from a source rock during natural sedimentary processes. The minerals, weathered from rocks or veins, are washed out by streams and mixed with alluvial deposits of sand or gravel, from which they can then be extracted by placer mining. 2.
A very large body of igneous rock, usually granite, which has been exposed by erosion of the overlying rock. [2] bathymetry 1. The measurement of water depth, mainly of seas and oceans but sometimes of deep lakes. 2. The study and depiction of the physical features or relief of the floor of a lake or ocean.
Rock can also form in the absence of a substantial pressure gradient as material that condensed from a protoplanetary disk, without ever undergoing any transformations in the interior of a large object such as a planet or moon. Astrophysicists classify this as a fourth type of rock: primitive rock. This type is common in asteroids and meteorites.
Rocks can also be composed entirely of non-mineral material; coal is a sedimentary rock composed primarily of organically derived carbon. [34] [38] In rocks, some mineral species and groups are much more abundant than others; these are termed the rock-forming minerals.
A conglomerate or any clastic sedimentary rock that consists of a single rock or mineral is known as either a monomict, monomictic, oligomict, or oligomictic conglomerate. If the conglomerate consists of two or more different types of rocks, minerals, or combination of both, it is known as either a polymict or polymictic conglomerate.