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| name = Gedrite
| name = Gedrite
| category = Inosilicate, ferromagnesian amphibole group
| category = Inosilicate, ferromagnesian amphibole group
| image =
| image = Gedrite-Magnetite-448448.jpg
| caption =
| caption = Gedrite on a [[feldspar]] [[matrix (geology)|matrix]]
| formula = Mg<sub>2</sub>(Mg<sub>3</sub>Al<sub>2</sub>)(Si<sub>6</sub>Al<sub>2</sub>)O<sub>22</sub>(OH)<sub>2</sub>
| formula = {{chem2|Mg2(Mg3Al2)(Si6Al2)O22(OH)2}}
| IMAsymbol = Ged<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref>
| strunz = 9.DD.05
| strunz = 9.DD.05
| system = [[Orthorhombic]]
| system = [[Orthorhombic]]
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| habit = Bladed and prismatic crystals; fibrous and sheath like aggregates.
| habit = Bladed and prismatic crystals; fibrous and sheath like aggregates.
| twinning = contact twinning
| twinning = contact twinning
| cleavage = 56 and 126° - good; {210} perfect
| cleavage = 56 and 126° – good; {210} perfect
| fracture = Splintery
| fracture = Splintery
| mohs = 5.5 - 6
| mohs = 5.5–6
| luster = Vitreous to silky
| luster = Vitreous to silky
| refractive = n<sub>α</sub> = 1.671 n<sub>β</sub> = 1.681 n<sub>γ</sub> = 1.690
| refractive = n<sub>α</sub> = 1.671 n<sub>β</sub> = 1.681 n<sub>γ</sub> = 1.690
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| 2V = Measured: 75°
| 2V = Measured: 75°
| streak =
| streak =
| gravity = 3.18 - 3.33
| gravity = 3.18–3.33
| density =
| density =
| melt =
| melt =

| [[Found]] = Found chiefly in Montana,Idaho,North Carolina, U.S.S.R., Japan, Scotland, Finland, and India
| fusibility =
| fusibility =
| diagnostic =
| diagnostic =
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| references = <ref name=Handbook>http://www.handbookofmineralogy.org/pdfs/gedrite.pdf Handbook of Mineralogy</ref><ref name=Webmin>http://webmineral.com/data/Gedrite.shtml Webmineral</ref><ref>http://www.mindat.org/min-1665.html Mindat</ref><ref>[http://pubsites.uws.edu.au/ima-cnmnc/ IMA Master List]</ref>
| references = <ref name=Handbook>http://www.handbookofmineralogy.org/pdfs/gedrite.pdf Handbook of Mineralogy</ref><ref name=Webmin>http://webmineral.com/data/Gedrite.shtml Webmineral</ref><ref>http://www.mindat.org/min-1665.html Mindat</ref><ref>[http://pubsites.uws.edu.au/ima-cnmnc/ IMA Master List]</ref>
}}
}}
'''Gedrite''' is a [[crystalline|crystal]] belonging to the [[crystal system|orthorhombic]] ferromagnesian subgroup of the [[amphibole]] supergroup of the double chain [[classification of minerals - Silicates|inosilicate]] minerals with the ideal formula: Mg<sub>2</sub>(Mg<sub>3</sub>Al<sub>2</sub>)(Si<sub>6</sub>Al<sub>2</sub>)O<sub>22</sub>(OH)<sub>2</sub>
'''Gedrite''' is a [[crystalline|crystal]] belonging to the [[crystal system|orthorhombic]] ferromagnesian subgroup of the [[amphibole]] supergroup of the double chain [[classification of minerals - Silicates|inosilicate]] minerals with the ideal chemical formula {{chem2|Mg2(Mg3Al2)(Si6Al2)O22(OH)2}}.


Gedrite is the [[magnesium]] (Mg) rich endmember of a [[solid solution]] series, with [[divalent]] magnesium [[cation]]s readily replaced with [[ferrous]] [[iron]] (Fe), leading to the iron rich endmember 'ferrogedrite', with the formula: Fe<sup>2+</sup><sub>2</sub>(Fe<sup>2+</sup><sub>3</sub>Al<sub>2</sub>)(Si<sub>6</sub>Al<sub>2</sub>)O<sub>22</sub>(OH)<sub>2</sub>. However, pure endmembers are very rare, with often either one of the mentioned cations dominating the composition. Thus, the formula can be written in such a way to express common intermediary gerdite samples:
Gedrite is the [[magnesium]] (Mg) rich [[endmember]] of a [[solid solution]] series, with [[divalent]] magnesium [[cation]]s readily replaced with [[ferrous]] [[iron]] (Fe), leading to the iron rich endmember 'ferrogedrite', with the formula: {{chem2|Fe^{2+}2(Fe^{2+}3Al2)(Si6Al2)O22(OH)2}}. However, pure endmembers are very rare, with often either one of the mentioned cations dominating the composition. Thus, the formula can be written in such a way to express common intermediary gedrite samples:
{{chem2|(Mg,Fe)^{2+}2(Mg,Fe)^{2+}3Al2(Al2Si6O22)(OH)2}}.
(Mg,Fe)<sup>2+</sup><sub>2</sub>(Mg,Fe)<sup>2+</sup><sub>3</sub>Al<sub>2</sub>(Al<sub>2</sub>Si<sub>6</sub>O<sub>22</sub>)(OH)<sub>2</sub>.


Divalent [[manganese]] (Mn) may substitute for some of the magnesium. Trivalent or [[ferric]] iron, or [[titanium]]<sup>4+</sup> may replace some of the [[aluminum]] (Al). [[Fluorine]] and [[chlorine]] are common substitutes for the [[hydroxyl]] (OH) in amphoboles. Other chemical impurites may include [[calcium]], [[sodium]], and [[potassium]].
Divalent [[manganese]] (Mn) may substitute for some of the magnesium. Trivalent or [[ferric]] iron, or [[titanium]]<sup>4+</sup> may replace some of the [[aluminum]] (Al). [[Fluorine]] and [[chlorine]] are common substitutes for the [[hydroxyl]] (OH) in amphoboles. Other chemical impurities may include [[calcium]], [[sodium]], and [[potassium]].


Gedrite also forms a series with another ferromagnesian amphibole, [[anthophyllite]].
Gedrite also forms a series with another ferromagnesian amphibole, [[anthophyllite]].
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Gedrite occurs in [[Contact metamorphism|contact]] and medium to high grade [[metamorphic rock]]s in association with [[garnet]], [[cordierite]], [[anthophyllite]], [[cummingtonite]], [[sapphirine]], [[sillimanite]], [[kyanite]], [[quartz]], [[staurolite]] and [[biotite]].<ref name=Handbook/>
Gedrite occurs in [[Contact metamorphism|contact]] and medium to high grade [[metamorphic rock]]s in association with [[garnet]], [[cordierite]], [[anthophyllite]], [[cummingtonite]], [[sapphirine]], [[sillimanite]], [[kyanite]], [[quartz]], [[staurolite]] and [[biotite]].<ref name=Handbook/>


Gedrite was first described for an occurrence in Gedres, France in 1836.<ref name=Webmin/>
Gedrite was first described for an occurrence in [[Gèdre]], [[Hautes-Pyrenees]], France in 1836.<ref name=Webmin/>


==References==
==References==
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[[Category:Amphibole group]]
[[Category:Amphibole group]]
[[Category:Orthorhombic minerals]]
[[Category:Orthorhombic minerals]]
[[Category:Minerals in space group 62]]




Latest revision as of 01:01, 4 January 2024

Gedrite
Gedrite on a feldspar matrix
General
CategoryInosilicate, ferromagnesian amphibole group
Formula
(repeating unit)		Mg2(Mg3Al2)(Si6Al2)O22(OH)2
IMA symbolGed[1]
Strunz classification9.DD.05
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPnma
Unit cella = 18.59, b = 17.89
c = 5.3 [Å]; Z = 4
Identification
ColorWhite, gray, brown, green, black
Crystal habitBladed and prismatic crystals; fibrous and sheath like aggregates.
Twinningcontact twinning
Cleavage56 and 126° – good; {210} perfect
FractureSplintery
Mohs scale hardness5.5–6
LusterVitreous to silky
DiaphaneityTranslucent, will transmit light on thin edges.
Specific gravity3.18–3.33
Optical propertiesBiaxial (+)
Refractive indexnα = 1.671 nβ = 1.681 nγ = 1.690
Birefringenceδ = 0.019
PleochroismWeak to moderate
2V angleMeasured: 75°
References[2][3][4][5]

Gedrite is a crystal belonging to the orthorhombic ferromagnesian subgroup of the amphibole supergroup of the double chain inosilicate minerals with the ideal chemical formula Mg2(Mg3Al2)(Si6Al2)O22(OH)2.

Gedrite is the magnesium (Mg) rich endmember of a solid solution series, with divalent magnesium cations readily replaced with ferrous iron (Fe), leading to the iron rich endmember 'ferrogedrite', with the formula: Fe2+2(Fe2+3Al2)(Si6Al2)O22(OH)2. However, pure endmembers are very rare, with often either one of the mentioned cations dominating the composition. Thus, the formula can be written in such a way to express common intermediary gedrite samples: (Mg,Fe)2+2(Mg,Fe)2+3Al2(Al2Si6O22)(OH)2.

Divalent manganese (Mn) may substitute for some of the magnesium. Trivalent or ferric iron, or titanium4+ may replace some of the aluminum (Al). Fluorine and chlorine are common substitutes for the hydroxyl (OH) in amphoboles. Other chemical impurities may include calcium, sodium, and potassium.

Gedrite also forms a series with another ferromagnesian amphibole, anthophyllite.

Gedrite occurs in contact and medium to high grade metamorphic rocks in association with garnet, cordierite, anthophyllite, cummingtonite, sapphirine, sillimanite, kyanite, quartz, staurolite and biotite.[2]

Gedrite was first described for an occurrence in Gèdre, Hautes-Pyrenees, France in 1836.[3]

References

[edit]
  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b http://www.handbookofmineralogy.org/pdfs/gedrite.pdf Handbook of Mineralogy
  3. ^ a b http://webmineral.com/data/Gedrite.shtml Webmineral
  4. ^ http://www.mindat.org/min-1665.html Mindat
  5. ^ IMA Master List


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