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A
mineral is a naturally occurring substance formed through
Geology processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties. A Rock (geology), by comparison, is an aggregate of minerals and need not have a specific chemical composition. Minerals range in composition from pure
chemical element and simple Salt (chemistry)s to very complex silicates with thousands of known forms.Klein, Cornelis and Cornelius Hurlbut, Jr. (1985)
Manual of Mineralogy, Wiley, 20th ed., ISBN 0-471-80580-7 The study of minerals is called mineralogy.
Mineral definition and classification
To be classified as a "true" mineral, a substance must be a
solid and have a
crystalline structure. It must also be a naturally occurring, homogeneous substance with a defined chemical composition. Traditional definitions excluded
organically derived material. However, the
International Mineralogical Association in 1995 adopted a new definition:
a mineral is an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes. http://www.minsocam.org/msa/ima/ima98(04).pdf Ernest H. Nickel, 1995,
The definition of a mineral, The Canadian Mineralogist, vol. 33, pp. 689 - 690
The modern classifications include an
organic class - in both the new Dana and the Strunz classification schemes. http://www.mindat.org/dana.php?a=50 Dana Classification 8th edition - ORGANIC COMPOUNDS http://www.mindat.org/strunz.php?a=9 Strunz Classification - Organic Compounds
The chemical composition may vary between
Endmember (mineralogy)s of a mineral system. For example the plagioclase feldspars comprise a continuous series from
sodium-rich
albite (NaAlSi3O8) to
calcium-rich
anorthite (CaAl2Si2O8) with four recognized intermediate compositions between. Mineral-like substances that don't strictly meet the definition are sometimes classified as mineraloids. Other natural-occurring substances are nonminerals. Industrial minerals is a market term and refers to commercially valuable mined materials (see also Minerals and Rocks section below).
A
crystal structure is the orderly geometric spatial arrangement of atoms in the internal structure of a mineral. There are 14 basic
crystal lattice arrangements of atoms in three dimensions, and these are referred to as the 14 "Bravais lattices". Each of these lattices can be classified into one of the six crystal systems, and all crystal structures currently recognized fit in one Bravais lattice and one crystal system. This crystal structure is based on regular internal atomic or
ionic arrangement that is often expressed in the geometric form that the crystal takes. Even when the mineral grains are too small to see or are irregularly shaped, the underlying crystal structure is always periodic, and can be determined by X-ray diffraction.
Chemistry and crystal structure together define a mineral. In fact, two or more minerals may have the same chemical composition, but differ in crystal structure (these are known as
polymorphs). For example, pyrite and
marcasite are both iron sulfide, but their arrangement of atoms differs. Similarly, some minerals have different chemical compositions, but the same crystal structure: for example,
halite (made from sodium and chlorine), galena (made from
lead and
sulfur) and
periclase (made from magnesium and oxygen) all share the same cubic crystal structure.
Crystal structure greatly influences a mineral's physical properties. For example, though
diamond and graphite have the same composition (both are pure carbon), graphite is very soft, while diamond is the hardest of all known minerals. This happens because the carbon atoms in graphite are arranged into sheets which can slide easily past each other, while the carbon atoms in diamond form a strong, interlocking three-dimensional network.
There are currently more than 4,000 known minerals, according to the
International Mineralogical Association, which is responsible for the approval of and naming of new mineral species found in nature. Of these, perhaps 150 can be called "common," 50 are "occasional," and the rest are "rare" to "extremely rare."
Differences between minerals and rocks
A mineral is a naturally occurring, inorganic solid with a definite chemical composition and a crystalline structure. A
Rock (geology) is an aggregate of one or more minerals. (A rock may also include organic remains and
mineraloids.) Some rocks are predominantly composed of just one mineral. For example, limestone is a sedimentary rock composed almost entirely of the mineral calcite. Other rocks contain many minerals, and the specific minerals in a rock can vary widely. Some minerals, like quartz, mica or feldspar are common, while others have been found in only one or two locations worldwide. The vast majority of the rocks of the Earth's crust consist of quartz, feldspar, mica,
chlorite, kaolin, calcite,
epidote,
olivine,
augite, hornblende, magnetite,
hematite, limonite and a few other minerals. Over half of the mineral species known are so rare that they have only been found in a handful of samples, and many are known from only one or two small grains.
Commercially valuable minerals and rocks are referred to as industrial minerals. Rocks from which minerals are Mining for economic purposes are referred to as
ores (the rocks and minerals that remain, after the desired mineral has been separated from the ore, are referred to as tailings).
Mineral composition of rocks
A main determining factor in the formation of minerals in a rock mass is the chemical composition of the mass, for a certain mineral can be formed only when the necessary elements are present in the rock. Calcite is most common in limestones, as these consist essentially of
calcium carbonate; quartz is common in sandstones and in certain igneous rocks which contain a high percentage of
silica.
Other factors are of equal importance in determining the natural association or paragenesis of rock-forming minerals, principally the mode of origin of the rock and the stages through which it has passed in attaining its present condition. Two rock masses may have very much the same bulk composition and yet consist of entirely different assemblages of minerals. The tendency is always for those compounds to be formed which are stable under the conditions under which the rock mass originated. A
granite arises by the consolidation of a molten
magma at high temperatures and great pressures and its component minerals are those stable under such conditions. Exposed to moisture, carbonic acid and other subaerial agents at the ordinary temperatures of the Earth's surface, some of these original minerals, such as quartz and white mica are relatively stable and remain unaffected; others
Weathering or decay and are replaced by new combinations. The
feldspar passes into
kaolinite,
muscovite and quartz, and any mafic minerals such as
pyroxenes,
amphiboles or biotite have been present they are often altered to chlorite, epidote, rutile and other substances. These changes are accompanied by disintegration, and the rock falls into a loose, incoherent, earthy mass which may be regarded as a sand or soil. The materials thus formed may be washed away and deposited as sandstone or siltstone. The structure of the original rock is now replaced by a new one; the mineralogical constitution is profoundly altered; but the bulk chemical composition may not be very different. The sedimentary rock may again undergo metamorphism. If penetrated by igneous rocks it may be recrystallized or, if subjected to enormous pressures with heat and movement during Orogeny, it may be converted into a
gneiss not very different in mineralogical composition though radically different in structure to the granite which was its original state.
Physical properties of minerals
Classifying minerals can range from simple to very difficult. A mineral can be identified by several physical properties, some of them being sufficient for full identification without equivocation. In other cases, minerals can only be classified by more complex chemical or X-ray diffraction analysis; these methods, however, can be costly and time-consuming.
Physical properties commonly used are:
- Crystal structure and habit: See the above discussion of crystal structure. A mineral may show good crystal habit or form, or it may be massive, granular or compact with only microscopically visible crystals.
- Hardness (materials science): the physical hardness of a mineral is usually measured according to the Mohs scale of mineral hardness. This scale is relative and goes from 1 to 10. Minerals with a given Mohs hardness can scratch the surface of any mineral that has a lower hardness than itself.
- Moh's Hardness scale:http://volcanoes.usgs.gov/Products/Pglossary/mineral.html USGS Photo glossary of volcano terms
- Talc Mg3Si4O10(OH)2
- Gypsum CaSO4·2H2O
- Calcite CaCO3
- Fluorite CaF2
- Apatite Ca5(PO4)3(OH,Cl,F)
- Orthoclase KAlSi3O8
- Quartz SiO2
- Topaz Al2SiO4(OH,F)2
- Corundum Al2O3
- Diamond C (pure carbon)
- Luster indicates the way a mineral's surface interacts with light and can range from dull to glassy (vitreous).
- Metallic -high reflectivity like metal: galena and pyrite
- Sub-metallic -slightly less than metallic reflectivity: magnetite
- Non-metallic lusters:
- Adamantine - brilliant, the luster of diamond also cerussite and anglesite
- Vitreous -the luster of a broken glass: quartz
- Pearly - iridescent and pearl-like: talc and apophyllite
- Resinous - the luster of resin: sphalerite and sulfur
- Silky - a soft light shown by fibrous materials: gypsum and chrysotile
- Dull/earthy -shown by finely crystallized minerals: the kidney ore variety of hematite
- Color indicates the appearance of the mineral in reflected light or transmitted light for translucent minerals (i.e. what it looks like to the naked eye).
- Iridescence - the play of colors due to surface or internal interference. Labradorite exhibits internal iridescence whereas hematite and sphalerite often show the surface effect.
- Streak (mineralogy) refers to the color of the powder a mineral leaves after rubbing it on an unglazed porcelain streak plate. Note that this is not always the same color as the original mineral.
- Cleavage (crystal) describes the way a mineral may split apart along various planes. In thin sections, cleavage is visible as thin parallel lines across a mineral.
- Fracture describes how a mineral breaks when broken contrary to its natural cleavage planes.
- Chonchoidal fracture is a smooth curved fracture with concentric ridges of the type shown by glass.
- Hackley is jagged fracture with sharp edges.
- Fibrous
- Irregular
- Specific gravity relates the mineral mass to the mass of an equal volume of water, namely the density of the material. While most minerals, including all the common rock-forming minerals, have a specific gravity of 2.5 - 3.5, a few are noticeably more or less dense, e.g. several sulfide minerals have high specific gravity compared to the common rock-forming minerals.
- Other properties: fluorescence (response to ultraviolet light), magnetism, radioactivity, Tenacity (geology) (response to mechanical induced changes of shape or form), piezoelectricity and reactivity to dilute acids.
Chemical properties of minerals
Minerals may be classified according to chemical composition. They are here categorized by anion group. The list below is in approximate order of their abundance in the Earth's
Crust (geology). The list follows the
James Dwight Dana classification system.http://www.minerals.net/mineral/sort-met.hod/dana/dana.htm Dana classification - Minerals.net
Silicate class
The largest group of minerals by far are the
Silicate minerals (most rocks are >95% silicates), which are composed largely of
silicon and oxygen, with the addition of ions such as aluminium, magnesium, iron, and calcium. Some important rock-forming silicates include the
feldspars, quartz,
olivines,
pyroxenes, amphiboles,
garnets, and micas.
Carbonate class
The
carbonate minerals consist of those minerals containing the anion (CO3)2- and include
calcite and
aragonite (both calcium carbonate), dolomite (magnesium/calcium carbonate) and
siderite (iron carbonate). Carbonates are commonly deposited in marine settings when the shells of dead
planktonic life settle and accumulate on the sea floor. Carbonates are also found in
evaporite settings (e.g. the Great Salt Lake, Utah) and also in karst regions, where the dissolution and reprecipitation of carbonates leads to the formation of caves, stalactites and stalagmites. The carbonate class also includes the nitrate and borate minerals.
==== Sulfate class ====
Sulfates all contain the sulfate anion, SO42-. Sulfates commonly form in
evaporite settings where highly saline waters slowly evaporate, allowing the formation of both sulfates and halides at the water-sediment interface. Sulfates also occur in
hydrothermal vein systems as gangue minerals along with
sulfide ore minerals. Another occurrence is as secondary oxidation products of original sulfide minerals. Common sulfates include anhydrite (calcium sulfate), Celestine (mineral) (strontium sulfate), barite (barium sulfate), and
gypsum (hydrated calcium sulfate). The sulfate class also includes the chromate, molybdate,
selenate,
sulfite, tellurate, and
tungstate minerals.
Halide class
The
halides are the group of minerals forming the natural
salts and include
fluorite (calcium fluoride), halite (sodium chloride),
sylvite (potassium chloride), and sal ammoniac (ammonium chloride). Halides, like sulfates, are commonly found in evaporitic settings such as Playas and landlocked seas such as the Dead Sea and Great Salt Lake. The halide class includes the fluoride,
chloride, and iodide minerals.
Oxide class
Oxides are extremely important in
mining as they form many of the
ores from which valuable metals can be extracted. They also carry the best record of changes in the
Earth's magnetic field. They commonly occur as precipitates close to the Earth's surface, oxidation products of other minerals in the near surface weathering zone, and as accessory minerals in igneous rocks of the crust and
Mantle (geology). Common oxides include
hematite (iron oxide), magnetite (iron oxide),
chromite (iron chromium oxide),
spinel (magnesium aluminium oxide - a common component of the mantle), ilmenite (iron titanium oxide), rutile (titanium dioxide), and ice (hydrogen oxide). The oxide class includes the oxide and the
hydroxide minerals.
==== Sulfide class ====Many
sulfide minerals are economically important as metal ores. Common sulfides include pyrite (iron sulfide - commonly known as
fools' gold),
chalcopyrite (copper iron sulfide),
pentlandite (nickel iron sulfide), and galena (lead sulfide). The sulfide class also includes the selenides, the tellurides, the
arsenides, the
antimonides, the bismuthinides, and the
sulfosalts (sulfur and a second anion such as arsenic).
Phosphate class
The
phosphate mineral group actually includes any mineral with a tetrahedral unit AO4 where A can be
phosphorus,
antimony, arsenic or vanadium. By far the most common phosphate is apatite which is an important
biology mineral found in teeth and bones of many animals. The phosphate class includes the phosphate, arsenate,
vanadate, and
antimonate minerals.
Element class
The Elemental group includes metals and intermetallic elements (gold, silver, copper), semi-metals and non-metals (antimony, bismuth, graphite, sulfur). This group also includes natural alloys, such as electrum (a natural alloy of gold and silver), phosphides, silicides, nitrides and carbides (which are usually only found naturally in a few rare meteorites).
Organic class
The organic mineral class includes biogenic substances in which geological processes have been a part of the genesis or origin of the existing compound. Minerals of the organic class include various oxalates, mellitates, citrates, cyanates, acetates, formates, hydrocarbons and other miscellaneous species.Examples include whewellite, moolooite, mellite, fichtelite, carpathite,
evenkite and
abelsonite.
See also
- List of minerals with associated Wikipedia articles
- List of minerals (complete)
- Tucson Gem & Mineral Show
- Industrial minerals
- Mineral water, water containing minerals or other dissolved substances that alter its taste or give it therapeutic value
- Mineral wool
- Mining
- Norman L. Bowen
- Quarry
- Dietary mineral
- Rocks
External links
- Minerals.net
- mindat.org Mindat database
- Webmineral.com
- Mineral atlas with properties, photos
References
A
mineral is a naturally occurring substance formed through
Geology processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties. A
Rock (geology), by comparison, is an aggregate of minerals and need not have a specific chemical composition. Minerals range in composition from pure chemical element and simple
Salt (chemistry)s to very complex silicates with thousands of known forms.Klein, Cornelis and Cornelius Hurlbut, Jr. (1985)
Manual of Mineralogy, Wiley, 20th ed., ISBN 0-471-80580-7 The study of minerals is called mineralogy.
Mineral definition and classification
To be classified as a "true" mineral, a substance must be a solid and have a crystalline structure. It must also be a naturally occurring, homogeneous substance with a defined chemical composition. Traditional definitions excluded
organically derived material. However, the
International Mineralogical Association in 1995 adopted a new definition:
a mineral is an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes. http://www.minsocam.org/msa/ima/ima98(04).pdf Ernest H. Nickel, 1995,
The definition of a mineral, The Canadian Mineralogist, vol. 33, pp. 689 - 690
The modern classifications include an
organic class - in both the new Dana and the Strunz classification schemes. http://www.mindat.org/dana.php?a=50 Dana Classification 8th edition - ORGANIC COMPOUNDS http://www.mindat.org/strunz.php?a=9 Strunz Classification - Organic Compounds
The
chemical composition may vary between Endmember (mineralogy)s of a mineral system. For example the
plagioclase feldspars comprise a continuous series from
sodium-rich albite (NaAlSi3O8) to
calcium-rich anorthite (CaAl2Si2O8) with four recognized intermediate compositions between. Mineral-like substances that don't strictly meet the definition are sometimes classified as mineraloids. Other natural-occurring substances are nonminerals. Industrial minerals is a market term and refers to commercially valuable mined materials (see also Minerals and Rocks section below).
A
crystal structure is the orderly geometric spatial arrangement of atoms in the internal structure of a mineral. There are 14 basic crystal lattice arrangements of atoms in three dimensions, and these are referred to as the 14 "
Bravais lattices". Each of these lattices can be classified into one of the six crystal systems, and all crystal structures currently recognized fit in one Bravais lattice and one crystal system. This crystal structure is based on regular internal atomic or
ionic arrangement that is often expressed in the geometric form that the crystal takes. Even when the mineral grains are too small to see or are irregularly shaped, the underlying crystal structure is always periodic, and can be determined by X-ray diffraction.
Chemistry and crystal structure together define a mineral. In fact, two or more minerals may have the same chemical composition, but differ in crystal structure (these are known as
polymorphs). For example, pyrite and
marcasite are both iron sulfide, but their arrangement of atoms differs. Similarly, some minerals have different chemical compositions, but the same crystal structure: for example,
halite (made from sodium and
chlorine), galena (made from
lead and
sulfur) and periclase (made from magnesium and oxygen) all share the same cubic crystal structure.
Crystal structure greatly influences a mineral's physical properties. For example, though
diamond and graphite have the same composition (both are pure carbon), graphite is very soft, while diamond is the hardest of all known minerals. This happens because the carbon atoms in graphite are arranged into sheets which can slide easily past each other, while the carbon atoms in diamond form a strong, interlocking three-dimensional network.
There are currently more than 4,000 known minerals, according to the International Mineralogical Association, which is responsible for the approval of and naming of new mineral species found in nature. Of these, perhaps 150 can be called "common," 50 are "occasional," and the rest are "rare" to "extremely rare."
Differences between minerals and rocks
A mineral is a naturally occurring, inorganic solid with a definite chemical composition and a crystalline structure. A
Rock (geology) is an aggregate of one or more minerals. (A rock may also include organic remains and
mineraloids.) Some rocks are predominantly composed of just one mineral. For example, limestone is a
sedimentary rock composed almost entirely of the mineral calcite. Other rocks contain many minerals, and the specific minerals in a rock can vary widely. Some minerals, like quartz, mica or feldspar are common, while others have been found in only one or two locations worldwide. The vast majority of the rocks of the Earth's crust consist of quartz, feldspar, mica, chlorite,
kaolin, calcite, epidote, olivine,
augite, hornblende,
magnetite, hematite,
limonite and a few other minerals. Over half of the mineral species known are so rare that they have only been found in a handful of samples, and many are known from only one or two small grains.
Commercially valuable minerals and rocks are referred to as
industrial minerals. Rocks from which minerals are
Mining for economic purposes are referred to as ores (the rocks and minerals that remain, after the desired mineral has been separated from the ore, are referred to as tailings).
Mineral composition of rocks
A main determining factor in the formation of minerals in a rock mass is the chemical composition of the mass, for a certain mineral can be formed only when the necessary elements are present in the rock. Calcite is most common in
limestones, as these consist essentially of calcium carbonate; quartz is common in sandstones and in certain igneous rocks which contain a high percentage of
silica.
Other factors are of equal importance in determining the natural association or
paragenesis of rock-forming minerals, principally the mode of origin of the rock and the stages through which it has passed in attaining its present condition. Two rock masses may have very much the same bulk composition and yet consist of entirely different assemblages of minerals. The tendency is always for those compounds to be formed which are stable under the conditions under which the rock mass originated. A granite arises by the consolidation of a molten magma at high temperatures and great pressures and its component minerals are those stable under such conditions. Exposed to moisture,
carbonic acid and other subaerial agents at the ordinary temperatures of the Earth's surface, some of these original minerals, such as quartz and white mica are relatively stable and remain unaffected; others
Weathering or decay and are replaced by new combinations. The
feldspar passes into
kaolinite,
muscovite and quartz, and any
mafic minerals such as
pyroxenes,
amphiboles or
biotite have been present they are often altered to chlorite, epidote,
rutile and other substances. These changes are accompanied by disintegration, and the rock falls into a loose, incoherent, earthy mass which may be regarded as a sand or soil. The materials thus formed may be washed away and deposited as sandstone or siltstone. The structure of the original rock is now replaced by a new one; the mineralogical constitution is profoundly altered; but the bulk chemical composition may not be very different. The sedimentary rock may again undergo
metamorphism. If penetrated by igneous rocks it may be recrystallized or, if subjected to enormous pressures with heat and movement during Orogeny, it may be converted into a gneiss not very different in mineralogical composition though radically different in structure to the granite which was its original state.
Physical properties of minerals
Classifying minerals can range from simple to very difficult. A mineral can be identified by several physical properties, some of them being sufficient for full identification without equivocation. In other cases, minerals can only be classified by more complex chemical or
X-ray diffraction analysis; these methods, however, can be costly and time-consuming.
Physical properties commonly used are:
- Crystal structure and habit: See the above discussion of crystal structure. A mineral may show good crystal habit or form, or it may be massive, granular or compact with only microscopically visible crystals.
- Hardness (materials science): the physical hardness of a mineral is usually measured according to the Mohs scale of mineral hardness. This scale is relative and goes from 1 to 10. Minerals with a given Mohs hardness can scratch the surface of any mineral that has a lower hardness than itself.
- Moh's Hardness scale:http://volcanoes.usgs.gov/Products/Pglossary/mineral.html USGS Photo glossary of volcano terms
- Talc Mg3Si4O10(OH)2
- Gypsum CaSO4·2H2O
- Calcite CaCO3
- Fluorite CaF2
- Apatite Ca5(PO4)3(OH,Cl,F)
- Orthoclase KAlSi3O8
- Quartz SiO2
- Topaz Al2SiO4(OH,F)2
- Corundum Al2O3
- Diamond C (pure carbon)
- Luster indicates the way a mineral's surface interacts with light and can range from dull to glassy (vitreous).
- Metallic -high reflectivity like metal: galena and pyrite
- Sub-metallic -slightly less than metallic reflectivity: magnetite
- Non-metallic lusters:
- Adamantine - brilliant, the luster of diamond also cerussite and anglesite
- Vitreous -the luster of a broken glass: quartz
- Pearly - iridescent and pearl-like: talc and apophyllite
- Resinous - the luster of resin: sphalerite and sulfur
- Silky - a soft light shown by fibrous materials: gypsum and chrysotile
- Dull/earthy -shown by finely crystallized minerals: the kidney ore variety of hematite
- Color indicates the appearance of the mineral in reflected light or transmitted light for translucent minerals (i.e. what it looks like to the naked eye).
- Iridescence - the play of colors due to surface or internal interference. Labradorite exhibits internal iridescence whereas hematite and sphalerite often show the surface effect.
- Streak (mineralogy) refers to the color of the powder a mineral leaves after rubbing it on an unglazed porcelain streak plate. Note that this is not always the same color as the original mineral.
- Cleavage (crystal) describes the way a mineral may split apart along various planes. In thin sections, cleavage is visible as thin parallel lines across a mineral.
- Fracture describes how a mineral breaks when broken contrary to its natural cleavage planes.
- Chonchoidal fracture is a smooth curved fracture with concentric ridges of the type shown by glass.
- Hackley is jagged fracture with sharp edges.
- Fibrous
- Irregular
- Specific gravity relates the mineral mass to the mass of an equal volume of water, namely the density of the material. While most minerals, including all the common rock-forming minerals, have a specific gravity of 2.5 - 3.5, a few are noticeably more or less dense, e.g. several sulfide minerals have high specific gravity compared to the common rock-forming minerals.
- Other properties: fluorescence (response to ultraviolet light), magnetism, radioactivity, Tenacity (geology) (response to mechanical induced changes of shape or form), piezoelectricity and reactivity to dilute acids.
Chemical properties of minerals
Minerals may be classified according to chemical composition. They are here categorized by anion group. The list below is in approximate order of their abundance in the Earth's
Crust (geology). The list follows the
James Dwight Dana classification system.http://www.minerals.net/mineral/sort-met.hod/dana/dana.htm Dana classification - Minerals.net
Silicate class
The largest group of minerals by far are the
Silicate minerals (most rocks are >95% silicates), which are composed largely of silicon and
oxygen, with the addition of ions such as
aluminium, magnesium,
iron, and calcium. Some important rock-forming silicates include the feldspars,
quartz, olivines,
pyroxenes, amphiboles,
garnets, and
micas.
Carbonate class
The
carbonate minerals consist of those minerals containing the anion (CO3)2- and include
calcite and
aragonite (both calcium carbonate), dolomite (magnesium/calcium carbonate) and siderite (iron carbonate). Carbonates are commonly deposited in marine settings when the shells of dead planktonic life settle and accumulate on the sea floor. Carbonates are also found in evaporite settings (e.g. the Great Salt Lake,
Utah) and also in karst regions, where the dissolution and reprecipitation of carbonates leads to the formation of caves, stalactites and
stalagmites. The carbonate class also includes the
nitrate and borate minerals.
==== Sulfate class ====
Sulfates all contain the sulfate anion, SO42-. Sulfates commonly form in
evaporite settings where highly saline waters slowly evaporate, allowing the formation of both sulfates and halides at the water-sediment interface. Sulfates also occur in
hydrothermal vein systems as gangue minerals along with sulfide
ore minerals. Another occurrence is as secondary oxidation products of original sulfide minerals. Common sulfates include anhydrite (calcium sulfate),
Celestine (mineral) (strontium sulfate), barite (barium sulfate), and
gypsum (hydrated calcium sulfate). The sulfate class also includes the chromate,
molybdate,
selenate, sulfite, tellurate, and tungstate minerals.
Halide class
The
halides are the group of minerals forming the natural
salts and include fluorite (calcium fluoride), halite (sodium chloride), sylvite (potassium chloride), and
sal ammoniac (ammonium chloride). Halides, like sulfates, are commonly found in evaporitic settings such as Playas and landlocked seas such as the Dead Sea and Great Salt Lake. The halide class includes the
fluoride,
chloride, and
iodide minerals.
Oxide class
Oxides are extremely important in mining as they form many of the
ores from which valuable metals can be extracted. They also carry the best record of changes in the Earth's magnetic field. They commonly occur as precipitates close to the Earth's surface, oxidation products of other minerals in the near surface
weathering zone, and as accessory minerals in igneous rocks of the crust and
Mantle (geology). Common oxides include
hematite (iron oxide), magnetite (iron oxide),
chromite (iron chromium oxide),
spinel (magnesium aluminium oxide - a common component of the mantle),
ilmenite (iron titanium oxide), rutile (titanium dioxide), and
ice (hydrogen oxide). The oxide class includes the oxide and the hydroxide minerals.
==== Sulfide class ====Many
sulfide minerals are economically important as metal ores. Common sulfides include
pyrite (iron sulfide - commonly known as
fools' gold), chalcopyrite (copper iron sulfide),
pentlandite (nickel iron sulfide), and galena (lead sulfide). The sulfide class also includes the selenides, the tellurides, the arsenides, the
antimonides, the bismuthinides, and the sulfosalts (sulfur and a second anion such as arsenic).
Phosphate class
The
phosphate mineral group actually includes any mineral with a tetrahedral unit AO4 where A can be phosphorus, antimony, arsenic or
vanadium. By far the most common phosphate is apatite which is an important biology mineral found in teeth and bones of many animals. The phosphate class includes the phosphate, arsenate,
vanadate, and antimonate minerals.
Element class
The Elemental group includes metals and intermetallic elements (gold, silver, copper), semi-metals and non-metals (antimony, bismuth, graphite, sulfur). This group also includes natural alloys, such as electrum (a natural alloy of gold and silver), phosphides, silicides, nitrides and carbides (which are usually only found naturally in a few rare meteorites).
Organic class
The organic mineral class includes biogenic substances in which geological processes have been a part of the genesis or origin of the existing compound. Minerals of the organic class include various oxalates, mellitates, citrates, cyanates, acetates, formates, hydrocarbons and other miscellaneous species.Examples include whewellite,
moolooite,
mellite,
fichtelite,
carpathite,
evenkite and
abelsonite.
See also
External links
- Minerals.net
- mindat.org Mindat database
- Webmineral.com
- Mineral atlas with properties, photos
References
Minerals
Short descriptions and photographs of over a hundred different minerals and rocks. Projects for schools. ... Minerals This website gives short descriptions and photographs of over ...
Mineral - Wikipedia, the free encyclopedia
A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific ...
Dietary mineral - Wikipedia, the free encyclopedia
Dietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen which are present in common organic ...
Definition: mineral from Online Medical Dictionary
The Online Medical Dictionary is a searchable dictionary of definitions from medicine, science and technology.
Definition: minerals from Online Medical Dictionary
The Online Medical Dictionary is a searchable dictionary of definitions from medicine, science and technology.
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Minerals UK
Information on mineral exploration, mining, production and trade from the British Geological Survey Minerals Group.