Magnesiochloritoid
A valid IMA mineral species
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About Magnesiochloritoid
Formula:
MgAl2O(SiO4)(OH)2
Colour:
Colourless in thin section, pale blue-green in smaller crystals and dark blue in larger crystals
Hardness:
6½
Specific Gravity:
3.25
Crystal System:
Monoclinic
Member of:
Name:
Named as the Mg analogue of chloritoid. The name was originally published without IMA approval.
Monoclinic and triclinic polytypes are known.
Unique Identifiers
Mindat ID:
2497
Long-form identifier:
mindat:1:1:2497:2
IMA Classification of Magnesiochloritoid
Approved
IMA status notes:
Renamed by the IMA
First published:
1992
Approval history:
Renamed by the IMA in 1987. Other names such as magnesio-chloritoid, Mg-chloritoid and sismondine were recommended to be discarded in favor of magnesiochloritoid.
Classification of Magnesiochloritoid
9.AF.85
9 : SILICATES (Germanates)
A : Nesosilicates
F : Nesosilicates with additional anions; cations in [4], [5] and/or only [6] coordination
9 : SILICATES (Germanates)
A : Nesosilicates
F : Nesosilicates with additional anions; cations in [4], [5] and/or only [6] coordination
52.3.3.2
52 : NESOSILICATES Insular SiO4 Groups and O,OH,F,H2O
3 : Insular SiO4 Groups and O, OH, F, and H2O with cations in [6] coordination only
52 : NESOSILICATES Insular SiO4 Groups and O,OH,F,H2O
3 : Insular SiO4 Groups and O, OH, F, and H2O with cations in [6] coordination only
16.7.4
16 : Silicates Containing Aluminum and other Metals
7 : Aluminosilicates of Mg
16 : Silicates Containing Aluminum and other Metals
7 : Aluminosilicates of Mg
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Mcld | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Mcd | The Canadian Mineralogist (2019) | The Canadian Mineralogist (2019) The Canadian Mineralogist list of symbols for rock- and ore-forming minerals (December 30, 2019). download |
Physical Properties of Magnesiochloritoid
Transparency:
Transparent
Colour:
Colourless in thin section, pale blue-green in smaller crystals and dark blue in larger crystals
Hardness:
6½ on Mohs scale
Cleavage:
Perfect
{001} perfect (by analogy to choritoid)
{001} perfect (by analogy to choritoid)
Density:
3.25(2) g/cm3 (Measured)
Comment:
Measured in heavy liquids.
Optical Data of Magnesiochloritoid
Type:
Biaxial (+)
RI values:
nα = 1.687(2) nβ = 1.690(2) nγ = 1.702(2)
2V:
Measured: 40° to 50°, Calculated: 53°
Max. Birefringence:
δ = 0.015
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Moderate
Dispersion:
r < v moderate
Pleochroism:
Weak
Comments:
Very faint, light blue, grey blue, yellowish.
Comments:
Refractive indices from Chopin et al. (1992) for type material.
Chemistry of Magnesiochloritoid
Mindat Formula:
MgAl2O(SiO4)(OH)2
Element Weights:
Crystallography of Magnesiochloritoid
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/b
Setting:
C2/c
Cell Parameters:
a = 9.460(1) Å, b = 5.471(1) Å, c = 18.182(2) Å
β = 101.4(1)°
β = 101.4(1)°
Ratio:
a:b:c = 1.729 : 1 : 3.323
Unit Cell V:
922.46 ų (Calculated from Unit Cell)
Z:
4
Twinning:
Common on {001}, polysynthetic.
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0007687 | Magnesiochloritoid | Comodi P, Mellini M, Zanazzi P F (1992) Magnesiochloritoid: compressibility and high pressure structure refinement Physics and Chemistry of Minerals 18 483-490 | 1992 | 0.0001 | 293 | ||
| 0007686 | Magnesiochloritoid | Comodi P, Mellini M, Zanazzi P F (1992) Magnesiochloritoid: compressibility and high pressure structure refinement Physics and Chemistry of Minerals 18 483-490 | 1992 | 0.0001 | 293 | ||
| 0001140 | Magnesiochloritoid | Ivaldi G, Catti M, Ferraris G (1988) Crystal structure at 25 and 700 C of magnesiochloritoid from a high-pressure assemblage (Monte Rosa) Sample at 700 C American Mineralogist 73 358-364 |  | 1988 | 0 | 293 | |
| 0001139 | Magnesiochloritoid | Ivaldi G, Catti M, Ferraris G (1988) Crystal structure at 25 and 700 C of magnesiochloritoid from a high-pressure assemblage (Monte Rosa) Sample at 25 C American Mineralogist 73 358-364 | | 1988 | 0 | 293 | |
| 0007688 | Magnesiochloritoid | Comodi P, Mellini M, Zanazzi P F (1992) Magnesiochloritoid: compressibility and high pressure structure refinement Physics and Chemistry of Minerals 18 483-490 | 1992 | 3.4 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.46 Å | (100) |
| 2.964 Å | (18) |
| 2.306 Å | (14) |
| 1.574 Å | (11) |
| 2.356 Å | (7) |
| 2.459 Å | (6) |
| 1.482 Å | (6) |
| 1.362 Å | (6) |
Comments:
Data from Chopin et al. (1992).
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 5: Initiation of plate tectonics | <3.5-2.5 |
| 39 : High-? metamorphism (blueschist, eclogite, ultrahigh ? facies) | |
| 40 : Regional metamorphism (greenschist, amphibolite, granulite facies) |
Type Occurrence of Magnesiochloritoid
Co-Type Localities:
General Appearance of Type Material:
Dark-blue millimetric crystals.
Place of Conservation of Type Material:
National School of Mines, Paris, France.
Museum of Natural Science, Torino, Italy.
Museum of Natural Science, Torino, Italy.
Geological Setting of Type Material:
In magnesian pelitic rocks (or magnesian microsystems in mafic rocks) metamorphosed at high pressures, near 15 kbar or more.
Associated Minerals at Type Locality:
Other Language Names for Magnesiochloritoid
Relationship of Magnesiochloritoid to other Species
Member of:
Other Members of Chloritoid Group:
| Carboirite | Fe2+Al2O(GeO4)(OH)2 | Tric. 1 |
| Chloritoid | Fe2+Al2O(SiO4)(OH)2 | Mon. 2/m : B2/b |
| Ottrélite | Mn2+Al2O(SiO4)(OH)2 | Mon. |
Common Associates
Associations Based on Photo Data:
Related Minerals - Strunz-mindat Grouping
| 9.AF. | Chegemite | Ca7(SiO4)3(OH)2 |
| 9.AF. | Jingwenite-(Y) | YAlV4+(SiO4)O2(OH)2 |
| 9.AF. | Barwoodite | Mn2+6Nb5+(SiO4)2O3(OH)3 |
| 9.AF.05 | Sillimanite | Al2(SiO4)O |
| 9.AF.05 | 'Xenolite' | Al10Si8O31 |
| 9.AF.10 | Kanonaite | Mn3+Al(SiO4)O |
| 9.AF.10 | Andalusite | Al2(SiO4)O |
| 9.AF.15 | Kyanite | Al2(SiO4)O |
| 9.AF.20 | Krieselite | Al2(GeO4)F2 |
| 9.AF.20 | Mullite | Al4+2xSi2-2xO10-x |
| 9.AF.23 | Boromullite | Al9BSi2O19 |
| 9.AF.25 | Yoderite | Mg(Al,Fe3+)3(SiO4)2O(OH) |
| 9.AF.30 | Zincostaurolite | Zn2Al9Si4O23(OH) |
| 9.AF.30 | Staurolite | Fe2+2Al9Si4O23(OH) |
| 9.AF.30 | Magnesiostaurolite | Mg(Mg,Li)3(Al,Mg)18Si8O44(OH)4 |
| 9.AF.35 | Topaz | Al2(SiO4)(F,OH)2 |
| 9.AF.40 | Norbergite | Mg3(SiO4)F2 |
| 9.AF.45 | Chondrodite | Mg5(SiO4)2F2 |
| 9.AF.45 | Kumtyubeite | Ca5(SiO4)2F2 |
| 9.AF.45 | Reinhardbraunsite | Ca5(SiO4)2(OH,F)2 |
| 9.AF.45 | Hydroxylchondrodite | Mg5(SiO4)2(OH)2 |
| 9.AF.45 | Alleghanyite | Mn2+5(SiO4)2(OH)2 |
| 9.AF.50 | 'Unnamed (Ca-analogue of Humite)' | Ca7(SiO4)4F2 |
| 9.AF.50 | Humite | Mg7(SiO4)3F2 |
| 9.AF.50 | Manganhumite | Mn2+7(SiO4)3(OH)2 |
| 9.AF.50 | 'Unnamed (OH-analogue of humite)' | Mg7(SiO4)3(OH)2 |
| 9.AF.50 | Fluorchegemite | Ca7(SiO4)3F2 |
| 9.AF.55 | Hydroxylclinohumite | Mg9(SiO4)4(OH)2 |
| 9.AF.55 | Clinohumite | Mg9(SiO4)4F2 |
| 9.AF.55 | Sonolite | Mn2+9(SiO4)4(OH)2 |
| 9.AF.60 | Leucophoenicite | Mn2+7(SiO4)3(OH)2 |
| 9.AF.65 | Ribbeite | Mn2+5(SiO4)2(OH)2 |
| 9.AF.70 | Jerrygibbsite | Mn2+9(SiO4)4(OH)2 |
| 9.AF.75 | Franciscanite | Mn2+6(V5+,◻)2(SiO4)2(O,OH)6 |
| 9.AF.75 | Scorticoite | Mn6(Sb,◻)Σ2(SiO4)2O3(OH)3 |
| 9.AF.75 | Welinite | Mn2+6(W6+,Mg)2(SiO4)2(O,OH)6 |
| 9.AF.75 | Örebroite | Mn2+3(Sb5+,Fe3+)(SiO4)(O,OH)3 |
| 9.AF.80 | Ellenbergerite | Mg6(Mg,Ti,Zr,◻)2(Al,Mg)6Si8O28(OH)10 |
| 9.AF.85 | Ottrélite | Mn2+Al2O(SiO4)(OH)2 |
| 9.AF.85 | Chloritoid | Fe2+Al2O(SiO4)(OH)2 |
| 9.AF.90 | Olmiite | CaMn2+[SiO3(OH)](OH) |
| 9.AF.90 | Poldervaartite | CaCa[SiO3(OH)](OH) |
| 9.AF.95 | Pilawite-(Y) | Ca2Y2Al4(SiO4)4O2(OH)2 |
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.
Internet Links for Magnesiochloritoid
mindat.org URL:
https://www.mindat.org/min-2497.html
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References for Magnesiochloritoid
Reference List:
Chopin, Christian (1983) Magnesiochloritoid, a key-mineral for the petrogenesis of high-grade pelitic blueschists. Bulletin de Minéralogie, 106 (6) 715-717 doi:10.3406/bulmi.1983.7692
Chopin, Christian; Monié, Patrick (1984) A unique magnesiochloritoid-bearing, high-pressure assemblage from the Monte Rosa, Western Alps: petrologic and 40Ar-39Ar radiometric study. Contributions to Mineralogy and Petrology, 87 (4). 388-398 doi:10.1007/bf00381295
Dunn, Pete J., Chao, George Y., Fleischer, Michael, Ferraiolo, James A., Langley, Richard H., Pabst, Adolf, Zilczer, Janet A. (1985) New mineral names. American Mineralogist, 70 (1-2) 214-221
Fejer, E. E. (1986) Thirty-fourth list of new mineral names. Mineralogical Magazine, 50 (358) 741-761 doi:10.1180/minmag.1986.050.358.28
Kienast, J. R., Messiga, B. (1987) Cr-rich Mg-chloritoid, a first record in high-pressure metagabbros from Monviso (Cottian Alps), Italy. Mineralogical Magazine, 51 (363) 681-687 doi:10.1180/minmag.1987.051.363.08
Ivaldi, Gabriella; Catti, Michele; Ferraris, Giovanni (1988) Crystal structure at 25 and 700 °C of magnesiochloritoid from a high-pressure assemblage (Monte Rosa). American Mineralogist, 73 (3-4). 358-364
Comodi, Paola, Mellini, Marcello, Zanazzi, Pier Francesco (1992) Magnesiochloritoid: Compressibility and high pressure structure refinement. Physics and Chemistry of Minerals, 18 (8) 483-490 doi:10.1007/bf00205262
Localities for Magnesiochloritoid
Showing 13 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
China | |
| Zhang et al. (2004) |
Indonesia | |
| Verdiansyah et al. (2022) |
Italy (TL) | |
| Chopin et al. (1992) |
| Dal Piaz et al. (2008) | |
| Piccoli et al. (2007) |
| Piccoli et al. (2007) |
| Lithos | |
| Kienast et al. (1987) +1 other reference |
Spain | |
| Goffe et al. (1989) |
| www.foro-minerales.com (n.d.) |
Switzerland (TL) | |
| Bearth (1963) +2 other references |
| Stalder et al. (1998) |
| Chopin et al. (1984) |
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Piccolo Ghiacciaio di Verra, Champoluc, Ayas, Aosta Valley, Italy