Search results
Results from the WOW.Com Content Network
The proportion of silica in rocks and minerals is a major factor in determining their names and properties. [7] Rock outcrop along a mountain creek near Orosí, Costa Rica. Rocks are classified according to characteristics such as mineral and chemical composition, permeability, texture of the constituent particles, and particle size.
This metamorphism causes changes in the mineral composition of the rocks; creates a foliation, or planar surface, that is related to mineral growth under stress. This can remove signs of the original textures of the rocks, such as bedding in sedimentary rocks, flow features of lavas , and crystal patterns in crystalline rocks .
The other minerals in the rock are termed accessory minerals, and do not greatly affect the bulk composition of the rock. Rocks can also be composed entirely of non-mineral material; coal is a sedimentary rock composed primarily of organically derived carbon. [34] [38]
Most rock forms at elevated temperature and pressure, and the minerals making up the rock are often chemically unstable in the relatively cool, wet, and oxidizing conditions typical of the Earth's surface. Chemical weathering takes place when water, oxygen, carbon dioxide, and other chemical substances react with rock to change its composition.
It is the study of how plants and animals stabilize minerals under biological control, and the sequencing of mineral replacement of those minerals after deposition. [16] It uses techniques from chemical mineralogy, especially isotopic studies, to determine such things as growth forms in living plants and animals [ 17 ] [ 18 ] as well as things ...
Depending on the environmental conditions present at the time of their formation, concretions can be created by either concentric or pervasive growth. [11] [12] In concentric growth, the concretion grows as successive layers of mineral precipitate around a central core. This process results in roughly spherical concretions that grow with time.
Textures of rocks provide insights, as documented in the early 1900s by Bowen's reaction series. [15] An example of such texture, related to fractioned crystallization, is intergranular (also known as intercumulus) textures that develop wherever a mineral crystallizes later than the surrounding matrix, hence filling the left-over interstitial ...
Metamorphic rocks once existed as igneous or sedimentary rocks, but have been subjected to varying degrees of pressure and heat within the Earth's crust. The processes involved will change the composition and fabric of the rock and their original nature is often hard to distinguish. Metamorphic rocks are typically found in areas of mountain ...