Search results
Results from the WOW.Com Content Network
The geological definition of mineral normally excludes compounds that occur only in living organisms. However, some minerals are often biogenic (such as calcite) or organic compounds in the sense of chemistry (such as mellite). Moreover, living organisms often synthesize inorganic minerals (such as hydroxylapatite) that also occur in rocks.
Minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species . Within a mineral species there may be variation in physical properties or minor amounts of impurities that are recognized by mineralogists or wider society as a mineral variety .
Apatite is also found in clastic sedimentary rock as grains eroded out of the source rock. [7] [8] Phosphorite is a phosphate-rich sedimentary rock containing as much as 80% apatite, [9] which is present as cryptocrystalline masses referred to as collophane. [10] Economic quantities of apatite are also sometimes found in nepheline syenite or in ...
Halite and sylvite commonly form as evaporites, and can be dominant minerals in chemical sedimentary rocks. Cryolite , Na 3 AlF 6 , is a key mineral in the extraction of aluminium from bauxites ; however, as the only significant occurrence at Ivittuut , Greenland , in a granitic pegmatite, was depleted, synthetic cryolite can be made from fluorite.
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. These physical properties are the result of the processes that formed the rocks. [5]
Kerogen is a complex mixture of organic chemical compounds that make up the most abundant fraction of organic matter in sedimentary rocks. [12] As kerogen is a mixture of organic materials, it is not defined by a single chemical formula. Its chemical composition varies substantially between and even within sedimentary formations.
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.
Calcium carbonate is a chemical compound with the chemical formula Ca CO 3. It is a common substance found in rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skeletons and pearls. Materials containing much calcium carbonate or resembling it are described as calcareous.