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Gedrite

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Formula:
☐{Mg2}{Mg3Al2}(Al2Si6O22)(OH)2
The gedrite group are orthorhombic amphiboles in the magnesium-iron-manganese amphibole subgroup defined with A(Na+K+2Ca)<0.5 apfu and C(Al+Fe3++2Ti)>1 apfu

Gedrite is defined with Mg2+ as the dominant cation both in the B and C2+ positions and Al in the C3+ position.
System:
Orthorhombic
Colour:
Pale greenish-grey to ...
Lustre:
Vitreous
Hardness:
5½ - 6
Name:
Named after the type locality at Gèdres, Héas Valley, France

Classification of Gedrite

Approved
8/F.12-100
9.DD.05

9 : SILICATES (Germanates)
D : Inosilicates
D : Inosilicates with 2-periodic double chains, Si4O11; Orthoamphiboles
66.1.2.5

66 : INOSILICATES Double-Width,Unbranched Chains,(W=2)
1 : Amphiboles - Mg-Fe-Mn-Li subgroup
16.19.18

16 : Silicates Containing Aluminum and other Metals
19 : Aluminosilicates of Fe and Mg
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http://www.mindat.org/min-1665.html
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First Recorded Occurrence of Gedrite

Year of Discovery:
1836

Physical Properties of Gedrite

Vitreous
Colour:
Pale greenish-grey to brown
Streak:
White
Hardness (Mohs):
5½ - 6

Crystallography of Gedrite

Crystal System:
Orthorhombic
Cell Parameters:
a = 18.59Å, b = 17.89Å, c = 5.3Å
Ratio:
a:b:c = 1.039 : 1 : 0.296
Unit Cell Volume:
V 1,762.65 ų (Calculated from Unit Cell)
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Optical Data of Gedrite

Type:
Biaxial (-)
RI values:
nα = 1.671 nβ = 1.681 nγ = 1.690
2V:
Measured: 75° , Calculated: 86°
Max Birefringence:
δ = 0.019
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
High
Dispersion:
r > v strong

Chemical Properties of Gedrite

Formula:
☐{Mg2}{Mg3Al2}(Al2Si6O22)(OH)2

The gedrite group are orthorhombic amphiboles in the magnesium-iron-manganese amphibole subgroup defined with A(Na+K+2Ca)<0.5 apfu and C(Al+Fe3++2Ti)>1 apfu

Gedrite is defined with Mg2+ as the dominant cation both in the B and C2+ positions and Al in the C3+ position.
Essential elements:
All elements listed in formula:
Common Impurities:
Mn,Ca,Ti,Na,K

Relationship of Gedrite to other Species

Series:
Forms a series with Anthophyllite (see here)
Other Members of Group:
Ferro-gedrite☐{Fe22+}{Fe32+Al2}(Al2Si6O22)(OH)2
9.DD.05Ferro-anthophyllite☐{Fe22+}{Fe52+}(Si8O22)(OH)2
9.DD.05Ferro-gedrite☐{Fe22+}{Fe32+Al2}(Al2Si6O22)(OH)2
9.DD.05Holmquistite☐{Li2}{Mg3Al2}(Si8O22)(OH)2
9.DD.05Proto-ferro-suenoite☐{Mn22+}{Fe52+}(Si8O22)(OH)2
9.DD.05Sodicanthophyllite{Na}{Mg2}{Mg5}(AlSi7O22)(OH)2
9.DD.05Sodic-ferro-anthophyllite{Na}{Fe22+}{Fe52+}(AlSi7O22)(OH)2
9.DD.05Sodic-ferrogedrite{Na}{Fe22+}{Fe32+Al2}(Al3Si5O22)(OH)2
9.DD.05Sodicgedrite{Na}{Mg2}{Mg3Al2}(Al3Si5O22)(OH)2
9.DD.05Ferro-holmquistite☐{Li2}{Fe32+Al2}(Si8O22)(OH)2
9.DD.05Proto-anthophyllite☐{Mg2}{Mg5}(Si8O22)(OH)2
16.19.1IndialiteMg2Al3(AlSi5O18)
16.19.2Cordierite(Mg,Fe)2Al3(AlSi5O18)
16.19.3Sekaninaite(Fe,Mg)2Al3(AlSi5O18)
16.19.4Ferro-gedrite☐{Fe22+}{Fe32+Al2}(Al2Si6O22)(OH)2
16.19.5Staurolite(Fe2+,Mg,Zn)1.5-2Al9(SiO4)4O6(OH,O)2
16.19.6Chloritoid(Fe2+,Mg,Mn2+)Al2(SiO4)O(OH)2
16.19.7AmesiteMg2Al(AlSiO5)(OH)4
16.19.8Corundophilite(Mg,Fe,Al)6(Si,Al)4O10(OH)8
16.19.9YoderiteMg(Al,Fe3+)3(SiO4)2O(OH)
16.19.10Delessite(Mg,Fe,Fe,Al)(Si,Al)4O10(O,OH)8
16.19.11Ferrocarpholite(Fe2+,Mg)Al2(Si2O6)(OH)4
16.19.12Magnesiocarpholite(Mg,Fe2+)Al2(Si2O6)(OH)4
16.19.13Chamosite(Fe2+,Mg)5Al(AlSi3O10)(OH)8
16.19.14Orthochamosite(Fe2+,Mg,Fe3+)5Al(AlSi3O10)(OH,O)8
16.19.15Berthierine(Fe2+,Fe3+,Al)3(Si,Al)2O5(OH)4
16.19.16Odinite(Fe,Mg,Al,Fe,Ti,Mn)2.4((Si,Al)2O5)(OH)4
16.19.17Clinochlore(Mg,Fe2+)5Al(AlSi3O10)(OH)8
16.19.19Magnesiogedrite
16.19.20Diabantite(Mg,Fe,Al)6((Si,Al)4O10)(OH)8
16.19.21Sudoite(Mg,Fe2+)2Al3(AlSi3O10)(OH)8
16.19.22Vermiculite(Mg,Fe,Al)3((Al,Si)4O10)(OH)2 · 4H2O
16.19.23Corrensite(Mg,Fe)9((Si,Al)8O20)(OH)10 · nH2O

Other Names for Gedrite

Name in Other Languages:

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Gedrite

Reference List:
Mineralogical Record: 29: 169-174.

P. E. Champness and K. A. Rodgers (2000) The origin of iridescence in anthophyllite-gedrite from Simiuttat, Nuuk district, southern West Greenland. Mineralogical Magazine 64, 885-889.

Hawthorne, F. C. and Oberti, R. (2006) On the classification of amphiboles: Canadian Mineralogist 44, 1-21.

Schindler, M.; Sokolova, E.; Abdu, Y.; Hawthorne, F.C.; Evans, B.W.; Ishida, K. (2008) The crystal chemistry of the gedrite-group amphiboles. I. Crystal structure and site populations. Mineral. Mag., 72, 703-730.

Hawthorne, F.C.; Schindler, M.; Abdu, Y.; Sokolova, E.; Evans, B.W.; Ishida, K. (2008) The crystal chemistry of the gedrite-group amphiboles. II. Stereochemistry and chemical relations. Mineral. Mag., 72, 731-745.

Frank C. Hawthorne, Roberta Oberti, George E. Harlow, Walter V. Maresch, Robert F. Martin, John C. Schumacer, Mark D. Welch (2012): Nomenclature of the amphibole supergroup, American Mineralogist, Volume 97, pages 2031–2048

Internet Links for Gedrite

Localities for Gedrite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
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