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Feldspathoid
 
 
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The feldspathoids are a group of tectosilicate
Silicate minerals

The silicate minerals make up the largest and most important class of rock-forming minerals, comprising approximately 90 percent of the crust of the Earth....
 mineral
Mineral

A mineral is a naturally occurring solid formed through Geology processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties....
s which resemble feldspar
Feldspar

Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's Crust .Feldspars crystallize from magma in both intrusive and extrusive igneous rocks, as veins, and are also present in many types of metamorphic rock....
s but have a different structure and much lower silica content. They occur in rare and unusual types of igneous rock
Igneous rock

Igneous rock is one of the three main Rock types . Igneous rock is formed by magma being cooled and becoming solid . They may form with or without crystallization, either below the surface as Intrusion rocks or on the surface as extrusive rocks....
s.

Foid, contraction of the term feldspathoid, is applied to any igneous rock
Igneous rock

Igneous rock is one of the three main Rock types . Igneous rock is formed by magma being cooled and becoming solid . They may form with or without crystallization, either below the surface as Intrusion rocks or on the surface as extrusive rocks....
 containing up to 60% modal feldspathoid minerals. For example, a syenite
Syenite

Syenite is a coarse-grained intrusive igneous rock of the same general composition as granite but with the quartz either absent or present in relatively small amounts ....
 with significant nepheline present can be termed a ‘foid-bearing syenite’, or a ‘foid-syenite’.






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The feldspathoids are a group of tectosilicate
Silicate minerals

The silicate minerals make up the largest and most important class of rock-forming minerals, comprising approximately 90 percent of the crust of the Earth....
 mineral
Mineral

A mineral is a naturally occurring solid formed through Geology processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties....
s which resemble feldspar
Feldspar

Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's Crust .Feldspars crystallize from magma in both intrusive and extrusive igneous rocks, as veins, and are also present in many types of metamorphic rock....
s but have a different structure and much lower silica content. They occur in rare and unusual types of igneous rock
Igneous rock

Igneous rock is one of the three main Rock types . Igneous rock is formed by magma being cooled and becoming solid . They may form with or without crystallization, either below the surface as Intrusion rocks or on the surface as extrusive rocks....
s.

Foid, contraction of the term feldspathoid, is applied to any igneous rock
Igneous rock

Igneous rock is one of the three main Rock types . Igneous rock is formed by magma being cooled and becoming solid . They may form with or without crystallization, either below the surface as Intrusion rocks or on the surface as extrusive rocks....
 containing up to 60% modal feldspathoid minerals. For example, a syenite
Syenite

Syenite is a coarse-grained intrusive igneous rock of the same general composition as granite but with the quartz either absent or present in relatively small amounts ....
 with significant nepheline present can be termed a ‘foid-bearing syenite’, or a ‘foid-syenite’. Such terminology is used on the Streckeisen (QAPF
QAPF diagram

A QAPF diagram is a double triangle diagram which is used to classify igneous rocks based on mineralogy composition. The acronym, QAPF, stands for "Quartz, feldspar, Plagioclase, Feldspathoid "....
) classification of igneous rocks.

Feldspathoid Minerals

  • Leucite
    Leucite

    Leucite is a rock -forming mineral composed of potassium and aluminium Silicate minerals K[AlSi2O6]. Crystals have the form of cubic icositetrahedra but, as first observed by Sir David Brewster in 1821, they are not optically isotropic, and are therefore pseudo-cubic....
  • Nepheline
    Nepheline

    Nepheline, also called nephelite , is a feldspathoid: a silica-undersaturated aluminosilicate, Sodium3PotassiumAluminium4silicon4Oxygen16, that occurs in intrusive and volcanic rocks with low silica, and in their associated pegmatites....
  • Analcime
  • Cancrinite
    Cancrinite

    Cancrinite is a complex carbonate and silicate of sodium, calcium and aluminium with the formula sodium6calcium2[Found originally in 1839 in the Ural Mountains, it is named after Georg von Cancrin, a Russian minister of finance....
  • Hauyne
    Hauyne

    Hauyne, ha?yne or hauynite is a Silicate minerals mineral with sulfate and chloride with formula: 4-8Al6Si6241-2....
  • Lazurite
    Lazurite

    Lazurite is a Silicate minerals mineral with sulfate, sulfur and chloride with formula: 862. It is a feldspathoid and a member of the sodalite group....
  • Nosean
    Nosean

    Nosean, also known as Noselite, is a mineral of the feldspathoid group with formula: potassium8aluminum6silicon6oxygen24....
  • Sodalite
    Sodalite

    File:Sodalite peg.jpgSodalite is a rich royal blue mineral widely enjoyed as an ornamental stone. Although massive sodalite samples are opaque, crystals are usually transparent to translucent....