feldspar
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Feldspars are a group of rock-forming
aluminium
aluminium
tectosilicate
mineral
mineral
s, containing sodium, calcium, potassium or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldspars and the ''alkali'' (potassium-sodium) feldspars. Feldspars make up about 60% of the Earth's crust, and 41% of the Earth's continental crust by weight. The IMA
symbol A symbol is a mark, sign, or word In linguistics, a word of a spoken language can be defined as the smallest sequence of phonemes that can be uttered in isolation with semantic, objective or pragmatics, practical meaning (linguistics), meanin ...
for feldspar is Fsp. Feldspars
crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosco ...
lize from
magma 300px, Lava flow on Hawaii (island), Hawaii. Lava is the extrusive equivalent of magma. Magma (from Ancient Greek μάγμα (''mágma'') meaning "thick unguent") is the molten or semi-molten natural material from which all igneous rocks are form ...

magma
as both
intrusive Intrusive may refer to: * Intrusiveness, a typically unwelcome behavior, interrupting and disturbing to others * Intrusive rock; intrusion of molten magma leaving behind igneous rock * Saltwater intrusion, the movement of saline water into freshwa ...
and
extrusive A volcanic rock from Italy with a relatively large six-sided phenocryst (diameter about 1 mm) surrounded by a fine-grained groundmass, as seen in thin section under a petrographic microscope Extrusive rock refers to the mode of igneous volcanic ro ...
igneous Igneous rock (derived from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the p ...
rocks and are also present in many types of . Rock formed almost entirely of calcic
plagioclase . (unknown scale) Plagioclase is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagiocla ...
feldspar is known as
anorthosite Anorthosite is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group o ...
. Feldspars are also found in many types of
sedimentary rock Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentation ...

sedimentary rock
s.


Compositions

The feldspar group of minerals consists of
tectosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide) SiO2 is usually cons ...
s, silicate minerals in which silicon ions are linked by shared oxygen ions to form a three-dimensional network. Compositions of major elements in common feldspars can be expressed in terms of three endmembers: * endmember AlFeldspar
What is Feldspar?
Industrial Minerals Association. Retrieved on July 18, 2007.
*
albite Albite is a plagioclase feldspar Feldspars () are a group of rock-forming tectosilicate minerals that make up about 41% of the Earth's continental crust by weight. Feldspars crystallize from magma as both Intrusive rock, intrusive and extru ...
endmember AlSiO *
anorthite Anorthite is the calcium Calcium is a chemical element with the Symbol (chemistry), symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physic ...
endmember AlSiO
Solid solution A solid solution describes a family of materials which have a range of compositions (e.g. AxB1−x) and a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The word "solution" is used to desc ...

Solid solution
s between K-feldspar and albite are called alkali feldspar. Solid solutions between albite and anorthite are called
plagioclase . (unknown scale) Plagioclase is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagiocla ...
, or, more properly, plagioclase feldspar. Only limited solid solution occurs between K-feldspar and anorthite, and in the two other solid solutions,
immiscibility Miscibility () is the property of two substances to mix in all proportions (that is, to fully dissolve in each other at any concentration In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and c ...
occurs at temperatures common in the crust of the Earth. Albite is considered both a plagioclase and alkali feldspar. The ratio of alkali feldspar to plagioclase feldspar, together with the proportion of
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra, ...

quartz
, is the basis for the QAPF classification of igneous rock. Calcium-rich plagioclase is the first feldspar to crystallize from a cooling magma, but the plagioclase becomes increasingly sodium-rich as crystallization continues. This defines the continuous
Bowen's reaction series Within the field of geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of whic ...

Bowen's reaction series
. K-feldspar is the final feldspar to crystallize from the magma.


Alkali feldspars

Alkali feldspar Feldspars () are a group of rock-forming tectosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. ...
s are grouped into two types: those containing potassium in combination with sodium, aluminium, or silicon; and those where potassium is replaced by barium. The first of these include: *
orthoclase Orthoclase, or orthoclase feldspar ( endmember formula K AlSi3 O8), is an important tectosilicate mineral which forms igneous rock. The name is from the Ancient Greek Ancient Greek includes the forms of the Greek language used in ancien ...

orthoclase
(
monoclinic In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, froze ...

monoclinic
)"The Mineral Orthoclase"
Feldspar Amethyst Galleries, Inc. Retrieved on February 8, 2008.
*
sanidine Sanidine is the high temperature form of potassium Potassium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substa ...

sanidine
(monoclinic)"Sanidine Feldspar"
Feldspar Amethyst Galleries, Inc. Retrieved on February 8, 2008.
*
microcline Microcline (KAlSi3O8) is an important igneous rock Igneous rock (derived from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in ...

microcline
(
triclinic Image:Microcline.jpeg, 200px, An example of the triclinic crystals, microcline image:Triclinic.svg, 180px, Triclinic (a ≠ b ≠ c and α ≠ β ≠ γ ) In crystallography, the triclinic (or anorthic) crystal system is one of the 7 crystal syste ...

triclinic
)"Microcline Feldspar"
Feldspar Amethyst Galleries, Inc. Retrieved on February 8, 2008.
*
anorthoclase The mineral anorthoclase ((Na,K)AlSi3O8) is a crystalline solid solution in the alkali feldspar series, in which the sodium-aluminium silicate member exists in larger proportion. It typically consists of between 10 and 36 percent of KAlSi3O8 and ...
(triclinic) Potassium and sodium feldspars are not perfectly
miscible Miscibility () is the property of two substances to mix in all proportions (that is, to fully dissolve in each other at any concentration In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and c ...
in the melt at low temperatures, therefore intermediate compositions of the alkali feldspars occur only in higher temperature environments. Sanidine is stable at the highest temperatures, and microcline at the lowest.
Perthite and a first-order red plate. The K-feldspar host (orthoclase) appears orange, and albite exsolution lamellae appear yellow. Long dimension of field is 0.4 mm. Perthite is used to describe an intergrowth of two feldspar Feldspars () are a group ...
is a typical texture in alkali feldspar, due to exsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition. The perthitic textures in the alkali feldspars of many
granite Granite () is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools ...

granite
s can be seen with the naked eye. Microperthitic textures in crystals are visible using a light microscope, whereas cryptoperthitic textures can be seen only with an electron microscope.


Ammonium feldspar

Buddingtonite is an ammonium feldspar with the chemical formula: NH4AlSi3O8. It is a mineral associated with hydrothermal alteration of the primary feldspar minerals.


Barium feldspars

Barium feldspars form as the result of the substitution of barium for potassium in the mineral structure. Barium feldspars are sometimes classified as a separate group of feldspars, and sometimes they are classified as a sub-group of alkali feldspars. The barium feldspars are monoclinic and include the following: * celsian *
hyalophane Hyalophane or jaloallofane is a crystalline mineral, part of the feldspar Feldspars () are a group of rock-forming tectosilicate minerals that make up about 41% of the Earth's continental crust by weight. Feldspars crystallize from magma as ...


Plagioclase feldspars

The plagioclase feldspars are
triclinic Image:Microcline.jpeg, 200px, An example of the triclinic crystals, microcline image:Triclinic.svg, 180px, Triclinic (a ≠ b ≠ c and α ≠ β ≠ γ ) In crystallography, the triclinic (or anorthic) crystal system is one of the 7 crystal syste ...

triclinic
. The plagioclase series follows (with percent
anorthite Anorthite is the calcium Calcium is a chemical element with the Symbol (chemistry), symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physic ...
in parentheses): *
albite Albite is a plagioclase feldspar Feldspars () are a group of rock-forming tectosilicate minerals that make up about 41% of the Earth's continental crust by weight. Feldspars crystallize from magma as both Intrusive rock, intrusive and extru ...
(0 to 10) *
oligoclase Oligoclase is a rock-forming mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks o ...
(10 to 30) *
andesine Andesine is a silicate mineral Silicate minerals are rock-forming mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the ...
(30 to 50) *
labradorite Labradorite ((Ca, Na)(Al, Si)4O8) is a calcium-enriched feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, containing sodium, calcium, potassium or barium. The most common members of the feldspar group are the ' ...

labradorite
(50 to 70) *
bytownite Bytownite is a calcium rich member of the plagioclase solid solution series of feldspar minerals with composition between anorthite and labradorite. It is usually defined as having between 70 and 90%Anorthite, An (formula: (Ca0.7-0.9,Na0.3-0.1) anorthite Anorthite_is_the_calcium Calcium_is_a_chemical_element_with_the_Symbol_(chemistry),_symbol_Ca_and_atomic_number_20._As_an_alkaline_earth_metal,_calcium_is_a_reactive_metal_that_forms_a_dark_oxide-nitride_layer_when_exposed_to_air._Its_physic_...
_(90_to_100)_ Intermediate_compositions_of_plagioclase ._(unknown_scale) Plagioclase_is_a_series_of__Silicate_minerals#Tectosilicates,_tectosilicate_(framework_silicate)_minerals_within_the__feldspar_group._Rather_than_referring_to_a_particular_mineral_with_a_specific_chemical_composition,_plagiocla_...
_feldspar_also_may_Exsolution.html" ;"title="l(A ...
(70 to 90) *
anorthite Anorthite is the calcium Calcium is a chemical element with the Symbol (chemistry), symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physic ...
(90 to 100) Intermediate compositions of
plagioclase . (unknown scale) Plagioclase is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagiocla ...
feldspar also may Exsolution">exsolve to two feldspars of contrasting composition during cooling, but diffusion is much slower than in alkali feldspar, and the resulting two-feldspar intergrowths typically are too fine-grained to be visible with optical microscopes. The
immiscibility Miscibility () is the property of two substances to mix in all proportions (that is, to fully dissolve in each other at any concentration In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and c ...
gaps in the plagioclase solid solutions are complex compared to the gap in the alkali feldspars. The play of colors visible in some feldspar of
labradorite Labradorite ((Ca, Na)(Al, Si)4O8) is a calcium-enriched feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, containing sodium, calcium, potassium or barium. The most common members of the feldspar group are the ' ...

labradorite
composition is due to very fine-grained exsolution
lamellae Lamella (plural lamellae) means a small plate or flake in Latin, and in English may refer to: Biology * Lamella (mycology) File:Trompetenpfifferling Teufelskanzel.jpg, "False" gills of ''Craterellus tubaeformis'' A lamella, or gill, is a papery h ...
known as Bøggild intergrowth. The
specific gravity Relative density, or specific gravity, is the ratio In mathematics, a ratio indicates how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons ...
in the plagioclase series increases from
albite Albite is a plagioclase feldspar Feldspars () are a group of rock-forming tectosilicate minerals that make up about 41% of the Earth's continental crust by weight. Feldspars crystallize from magma as both Intrusive rock, intrusive and extru ...
(2.62) to
anorthite Anorthite is the calcium Calcium is a chemical element with the Symbol (chemistry), symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physic ...
(2.72–2.75).


Structure

The structure of a feldspar crystal is based on aluminosilicate tetrahedra. Each tetrahedron consists of an aluminium or silicon ion surrounded by four oxygen ions. Each oxygen ion, in turn, is shared by a neighbouring tetrahedron to form a three-dimensional network. The structure can be visualized as long chains of aluminosilicate tetrahedra, sometimes described as crankshaft chains because their shape is kinked. Each crankshaft chain links to neighbouring crankshaft chains to form a three-dimensional network of fused four-member rings. The structure is open enough for cations (typically sodium, potassium, or calcium) to fit into the structure and provide charge balance. File:Anorthite crankshaft.png, Diagram showing part of a crankshaft chain of feldspar File:Anorthite c.png, Feldspar crystal structure viewed along the c axis File:Anorthite a.png, Feldspar crystal structure viewed along the a axis File:Anorthite b.png, Feldspar crystal structure viewed along the b axis


Etymology

The name ''feldspar'' derives from the
German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also German nationality law * German language The German la ...

German
''Feldspat'', a compound of the words ''Feld'' ("field") and ''Spat'' ("flake"). ''Spat'' had long been used as the word for "a
rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition and the way in w ...
easily cleaved into flakes"; ''Feldspat'' was introduced in the 18th century as a more specific term, referring perhaps to its common occurrence in rocks found in fields (Urban Brückmann, 1783) or to its occurrence as "fields" within granite and other minerals (René-Just Haüy, 1804). The change from ''Spat'' to ''-spar'' was influenced by the English word ''spar'', meaning a non-opaque mineral with good cleavage. ''Feldspathic'' refers to materials that contain feldspar. The alternate spelling, ''felspar'', has fallen out of use. The term 'felsic', meaning light coloured minerals such as quartz and feldspars, is an acronymic word derived from ''fel''dspar and ''si''lica, unrelated to the redundant spelling 'felspar'.


Weathering

Chemical weathering Weathering is the breaking down of rocks, soil Soil (often stylized as SOiL) is an American rock band that was formed in Chicago (''City in a Garden''); I Will , image_map = , map_caption = Interactive maps of ...
of feldspars happens by
hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

hydrolysis
and produces
clay mineral Clay minerals are hydrous aluminium Aluminium (aluminum in American English, American and Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. Aluminium has a density lower than thos ...
s, including
illite Illite is a group of closely related non-expanding clay Clay is a type of fine-grained natural soil material containing clay minerals. Clays develop plasticity (physics), plasticity when wet, due to a molecular film of water surrounding the ...

illite
,
smectite Clay minerals are hydrous aluminium Aluminium (aluminum in American English, American and Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. Aluminium has a density lower than thos ...
, and
kaolinite Kaolinite ( ) is a clay mineral, with the chemical composition Aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4. It is an important industrial mineral. It is a layered silicate mineral, with one tetrahedron, tetrahedral sheet of silica () ...

kaolinite
. Hydrolysis of feldspars begins with the feldspar dissolving in water, which happens best in acidic or basic solutions and less well in neutral ones. The speed at which feldspars are weathered is controlled by how quickly they are dissolved. Dissolved feldspar reacts with H+ or OH ions and precipitates clays. The reaction also produces new
ion An ion () is a particle In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, localized physical body, object to which can be ascribed several physical property, physical or ...
s in solution, with the variety of ion controlled by the type of feldspar reacting. The abundance of feldspars in the Earth's crust means that clays are very abundant weathering products. About 40% of
mineral
mineral
s in
sedimentary rock Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentation ...

sedimentary rock
s are clays, and clays are the dominant minerals in the most common sedimentary rocks,
mudrock Mudrocks are a class of fine grained Sedimentary rock#Clastic sedimentary rocks, siliciclastic sedimentary rocks. The varying types of mudrocks include: ''siltstone'', ''claystone'', ''mudstone'', ''slate'', and ''shale''. Most of the particles of ...
s. They are also an important component of
soil File:Stagnogley.JPG, Surface-water-Gley soil, gley developed in glacial till, Northern Ireland. Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Earth's body of soil, called the pedosphere ...

soil
s. Feldspar that has been replaced by clay looks chalky compared to more crystalline and glassy unweathered feldspar grains. Feldspars, especially plagioclase feldspars, are not very stable at the earth's surface due to their high formation temperature. This lack of stability is why feldspars are easily weathered to clays. Because of this tendency to weather easily, feldspars are usually not prevalent in sedimentary rocks. Sedimentary rocks that contain large amounts of feldspar indicate that the sediment did not undergo much chemical weathering before being buried. This means it was probably
transported ''Transported'' is an Australian convict melodrama film directed by W. J. Lincoln. It is considered a lost film. Plot In England, Jessie Grey is about to marry Leonard Lincoln but the evil Harold Hawk tries to force her to marry him and she woun ...
a short distance in cold and/or dry conditions that didn't promote weathering, and that it was quickly buried by other sediment. Sandstones with large amounts of feldspar are called
arkose Arkose () is a detrital sedimentary rock Sedimentary rocks are types of Rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at the Earth's surface, followed by Cementation (geol ...

arkose
s.


Production and uses

About 20 million tonnes of feldspar were produced in 2010, mostly by three countries:
Italy Italy ( it, Italia ), officially the Italian Republic ( it, Repubblica Italiana, links=no ), is a country consisting of a Northern Italy, continental part, delimited by the Alps, a Italian Peninsula, peninsula and List of islands of Italy, se ...

Italy
(4.7 Mt),
Turkey Turkey ( tr, Türkiye ), officially the Republic of Turkey, is a country located mainly on Anatolia in Western Asia, with a small portion on the Balkans in Southeast Europe. It shares borders with Greece and Bulgaria to the northwest; the B ...

Turkey
(4.5 Mt), and
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the List of countries and dependencies by population, world's most populous country, with a population of around 1.4 billion. Covering approximately 9.6& ...

China
(2 Mt). Feldspar is a common raw material used in glassmaking, ceramics, and to some extent as a filler and extender in paint, plastics, and rubber. In glassmaking, alumina from feldspar improves product hardness, durability, and resistance to chemical corrosion. In ceramics, the alkalis in feldspar (
calcium oxide Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms fro ...

calcium oxide
,
potassium oxide Potassium oxide (K O) is an ionic compound of potassium Potassium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure ...
, and
sodium oxide Sodium oxide is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemi ...
) act as a flux, lowering the melting temperature of a mixture. Fluxes melt at an early stage in the
firing Dismissal (also referred to as firing) is the termination of employment Termination of employment is an employee's departure from a job and the end of an employee's duration with an employer. Termination may be voluntary on the employee's part, o ...
process, forming a glassy matrix that bonds the other components of the system together. In the US, about 66% of feldspar is consumed in glassmaking, including glass containers and glass fibre. Ceramics (including electrical insulators, sanitary ware, pottery, tableware, and tile) and other uses, such as fillers, accounted for the remainder.Apodaca, Lori E
Feldspar and nepheline syenite
USGS 2008 Minerals Yearbook
Bon Ami Bon Ami () is a brand of scouring powder sold by the Bon Ami Company of Kansas City, Missouri. Since its inception in the late 19th century, the brand's advertising campaigns have gained particular notice. History 19th century The original Bon ...
, which had a mine near Little Switzerland, North Carolina, used feldspar as an abrasive in its cleaners. The Little Switzerland Business Association says the McKinney Mine was the largest feldspar mine in the world, and North Carolina was the largest producer. Feldspar had been discarded in the process of mining mica until William Dibbell sent a premium quality product to the Ohio company Golding and Sons around 1910. In earth sciences and archaeology, feldspars are used for potassium-argon dating, argon-argon dating, and luminescence dating. In October 2012, the Mars Curiosity rover, ''Curiosity'' rover analysed a rock that turned out to have a high feldspar content.Nasa's Curiosity rover finds 'unusual rock'
(12 October 2012) BBC News.


Images

File:Feldspar-Group-170604.jpg, Specimen of rare plumbian (lead-rich) feldspar File:Beryl-Schorl-Feldspar-Group-288077.jpg, Perched on crystallized, white feldspar is an upright 4 cm Aquamarine (gemstone), aquamarine crystal File:Feldspar-Group-Moonstone-36971.jpg, Feldspar and moonstone, from Sonora, Mexico File:Schorl-Feldspar-Group-49985.jpg, Schorl crystal on a cluster of euhedral feldspar crystals File:PIA16217-MarsCuriosityRover-1stXRayView-20121017.jpg, First X-ray crystallography#Mineralogy and metallurgy, X-ray view of Martian soil—feldspar, pyroxenes, olivine revealed (Curiosity rover at "Rocknest (Mars), Rocknest", October 17, 2012). File:Lunar Ferroan Anorthosite (60025).jpg, Moon, Lunar ferrous
anorthosite Anorthosite is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group o ...
#60025 (
plagioclase . (unknown scale) Plagioclase is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagiocla ...
feldspar). Collected by Apollo 16 from the Geology of the Moon#Highlands and craters, Lunar Highlands near Descartes (crater), Descartes Crater. This sample is currently on display at the National Museum of Natural History in Washington, D.C.


See also

* * *Rainbow lattice sunstone


References

*


Further reading

* Bonewitz, Ronald Louis (2005). ''Rock and Gem''. New York: DK Publishing. .


External links

* {{Authority control Feldspar, Tectosilicates Triclinic minerals Monoclinic minerals Industrial minerals