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Minasgeraisite-(Y)
A discredited species name
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About Minasgeraisite-(Y)
Seal of Minas Gerais, Brazil
Formula:
(Ca2Y2)◻2(Be2B2)[SiO4]4(OH)4
Originally thought to have the formula CaBe2Y2Si2O10.
Colour:
Purple to lavender purple
Lustre:
Sub-Vitreous, Resinous, Dull
Hardness:
6 - 7
Specific Gravity:
4.29
Crystal System:
Triclinic
Member of:
Name:
After the type locality in the state of Minas Gerais, Brazil, plus the suffix "-(Y)" due to the dominance of yttrium in the composition.
First Recorded Locality:
Discredited (2023): finally proved to be an ordered intermediate between datolite and hingganite-(Y).
Gadolinite-Datolite Group.
Former status: "Approved species, but validity may be questionable (Demartin et al., 2001)". The validity was later confirmed, together with a rather strong redefinition, by Cooper & Hawthorne (2018). These authors suggest formation of a triclinic subgroup within the gadolinite-datolite group to which minasgeraisite-(Y) should belong.
The Bi-richest portions represent an intermediate member between datolite, hingganite-(Y) and a hypothetical end-member formulated as Bi2◻Be2Si2O8(OH)2.
Gadolinite-Datolite Group.
Former status: "Approved species, but validity may be questionable (Demartin et al., 2001)". The validity was later confirmed, together with a rather strong redefinition, by Cooper & Hawthorne (2018). These authors suggest formation of a triclinic subgroup within the gadolinite-datolite group to which minasgeraisite-(Y) should belong.
The Bi-richest portions represent an intermediate member between datolite, hingganite-(Y) and a hypothetical end-member formulated as Bi2◻Be2Si2O8(OH)2.
Unique Identifiers
Mindat ID:
2716
Long-form identifier:
mindat:1:1:2716:4
IMA Classification of Minasgeraisite-(Y)
Discredited
Approval year:
1983
Approval history:
Approved IMA 1983 (IMA 1983-090)
Discreditation: Atencio, D. (2023): Proposal 23-F
Discreditation: Atencio, D. (2023): Proposal 23-F
Classification of Minasgeraisite-(Y)
9.AJ.20
9 : SILICATES (Germanates)
A : Nesosilicates
J : Nesosilicates with BO3 triangles and/or B[4], Be[4] tetrahedra, cornersharing with SiO4
9 : SILICATES (Germanates)
A : Nesosilicates
J : Nesosilicates with BO3 triangles and/or B[4], Be[4] tetrahedra, cornersharing with SiO4
54.2.1b.6
54 : NESOSILICATES Borosilicates and Some Beryllosilicates
2 : Borosilicates and Some Beryllosilicates with B in [4] coordination
54 : NESOSILICATES Borosilicates and Some Beryllosilicates
2 : Borosilicates and Some Beryllosilicates with B in [4] coordination
14.3.15
14 : Silicates not Containing Aluminum
3 : Silicates of Be
14 : Silicates not Containing Aluminum
3 : Silicates of Be
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Mgr-Y | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Minasgeraisite-(Y)
Sub-Vitreous, Resinous, Dull
Transparency:
Transparent
Comment:
Usually subvitreous, but may form dull fine-grained coatings.
Colour:
Purple to lavender purple
Streak:
Very pale purple
Hardness:
6 - 7 on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
{100}, "a second good cleavage" also noted
{100}, "a second good cleavage" also noted
Fracture:
Irregular/Uneven
Density:
4.29 g/cm3 (Measured) 4.90 g/cm3 (Calculated)
Comment:
Calculated density for theoretically pure material
Optical Data of Minasgeraisite-(Y)
Type:
Biaxial (+)
RI values:
nα = 1.740 nβ = 1.754 nγ = 1.786
2V:
Measured: 50° to 72°, Calculated: 68°
Birefringence:
0.046
Max. Birefringence:
δ = 0.046
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:
Very High (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Dispersion:
r > v weak
Comments:
Colorless to pale grayish yellow
Chemistry of Minasgeraisite-(Y)
Mindat Formula:
(Ca2Y2)◻2(Be2B2)[SiO4]4(OH)4
Originally thought to have the formula CaBe2Y2Si2O10.
Originally thought to have the formula CaBe2Y2Si2O10.
Element Weights:
Crystallography of Minasgeraisite-(Y)
Crystal System:
Triclinic
Class (H-M):
1 - Pedial
Space Group:
P1
Cell Parameters:
a = 9.994(4) Å, b = 7.705(3) Å, c = 4.764(2) Å
α = 90.042(9)°, β = 90.218(14)°, γ = 90.034(9)°
α = 90.042(9)°, β = 90.218(14)°, γ = 90.034(9)°
Ratio:
a:b:c = 1.297 : 1 : 0.618
Unit Cell V:
366.84 ų (Calculated from Unit Cell)
Z:
2
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 5.99 Å | (30) |
| 3.71 Å | (30) |
| 3.41 Å | (30) |
| 3.11 Å | (100) |
| 2.83 Å | (100) |
| 2.54 Å | (90) |
| 2.25 Å | (30) |
| 2.19 Å | (30) |
Comments:
39-344
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 34 : Complex granite pegmatites |
First Recorded Occurrence of Minasgeraisite-(Y)
General Appearance of First Recorded Material:
Purple botryoidal clusters with minutely textured surface where crystal terminations meet.
Geological Setting of First Recorded Material:
With milarite in late stage crystallization of a granite pegmatite.
Associated Minerals at First Recorded Locality:
Synonyms of Minasgeraisite-(Y)
Relationship of Minasgeraisite-(Y) to other Species
Member of:
Other Members of Gadolinite Subgroup:
| Calcybeborosilite-(Y) | (Y,Ca)2(◻,Fe2+)(B,Be)2[SiO4]2(OH,O)2 | Mon. |
| Hingganite-(Ce) | (Ce,REE)2(◻,Fe2+)Be2[SiO4]2(OH)2 | Mon. 2/m : P21/c |
| Hingganite-(Nd) | Nd2◻Be2Si2O8(OH)2 | Mon. 2/m : P21/c |
| Hingganite-(Y) | (Y,REE,Ca)2(◻,Fe2+)Be2[SiO4]2(OH)2 | Mon. 2/m : P21/c |
| Hingganite-(Yb) | (Yb,Y,REE)2◻Be2[SiO4]2(OH)2 | Mon. 2/m : P21/c |
| 'Unnamed (OH-analogue of Gadolinite-(Y))' | (Y,Ca)2(Fe,◻)Be2Si2O8(OH,O)2 | Mon. 2/m |
Common Associates
Associations Based on Photo Data:
| 11 photos of Minasgeraisite-(Y) associated with Muscovite | KAl2(AlSi3O10)(OH)2 |
| 3 photos of Minasgeraisite-(Y) associated with Milarite | K(◻H2O)Ca2(Be2Al)[Si12O30] |
| 2 photos of Minasgeraisite-(Y) associated with Chernovite-(Y) | Y(AsO4) |
| 2 photos of Minasgeraisite-(Y) associated with Microcline | K(AlSi3O8) |
| 1 photo of Minasgeraisite-(Y) associated with Fluorite | CaF2 |
| 1 photo of Minasgeraisite-(Y) associated with Hingganite-(Y) | (Y,REE,Ca)2(◻,Fe2+)Be2[SiO4]2(OH)2 |
Related Minerals - Strunz-mindat Grouping
| 9.AJ. | Hingganite-(Nd) | Nd2◻Be2Si2O8(OH)2 |
| 9.AJ. | Arrheniusite-(Ce) | CaMg[(Ce7Y3)Ca5](SiO4)4(Si2B3AsO18)(BO3)F11 |
| 9.AJ.05 | Ominelite | (Fe2+,Mg)(Al,Fe3+)3(SiO4)(BO3)O2 |
| 9.AJ.05 | Grandidierite | (Mg,Fe2+)(Al,Fe3+)3(SiO4)(BO3)O2 |
| 9.AJ.10 | Dumortierite | Al(Al2O)(Al2O)2(SiO4)3(BO3) |
| 9.AJ.10 | Nioboholtite | (Nb0.6◻0.4)Al6BSi3O18 |
| 9.AJ.10 | Titanoholtite | (Ti0.75◻0.25)Al6BSi3O18 |
| 9.AJ.10 | Holtite | (Ta0.6◻0.4)Al6BSi3O18(O,OH)2.25 |
| 9.AJ.10 | Magnesiodumortierite | Mg(Al2OH)(Al2O)2(SiO4)3(BO3) |
| 9.AJ.15 | Garrelsite | Ba3NaSi2B7O16(OH)4 |
| 9.AJ.20 | 'Muromontite' | near Be2FeY2Si3O12 |
| 9.AJ.20 | Gadolinite-(Nd) | Nd2Fe2+Be2O2(SiO4)2 |
| 9.AJ.20 | Datolite | CaB(SiO4)(OH) |
| 9.AJ.20 | Melanocerite-(Ce) | (Ce,Ca)5(SiO4,BO4)3(OH,O) |
| 9.AJ.20 | Gadolinite-(Ce) | Fe2+Be2Ce3+2(SiO4)2O2 |
| 9.AJ.20 | Gadolinite-(Y) | Y2Fe2+Be2Si2O10 |
| 9.AJ.20 | 'Unnamed (OH-analogue of Gadolinite-(Y))' | (Y,Ca)2(Fe,◻)Be2Si2O8(OH,O)2 |
| 9.AJ.20 | Hingganite-(Ce) | (Ce,REE)2(◻,Fe2+)Be2[SiO4]2(OH)2 |
| 9.AJ.20 | Hingganite-(Y) | (Y,REE,Ca)2(◻,Fe2+)Be2[SiO4]2(OH)2 |
| 9.AJ.20 | Hingganite-(Yb) | (Yb,Y,REE)2◻Be2[SiO4]2(OH)2 |
| 9.AJ.20 | Homilite | Ca2(Fe2+,Mg)B2Si2O10 |
| 9.AJ.20 | Calcybeborosilite-(Y) | (Y,Ca)2(◻,Fe2+)(B,Be)2[SiO4]2(OH,O)2 |
| 9.AJ.25 | Stillwellite-(La) | LaBSiO5 |
| 9.AJ.25 | Stillwellite-(Ce) | (Ce,La,Ca)BSiO5 |
| 9.AJ.30 | Cappelenite-(Y) | Ba(Y,Ce)6Si3B6O24F2 |
| 9.AJ.35 | Laptevite-(Ce) | Ca6(Fe2+,Mn2+)Y3REE7(SiO4)3(PO4)(B3Si3O18)(BO3)F11 |
| 9.AJ.35 | Proshchenkoite-(Y) | Ca(Y,REE,Ca,Na,Mn)15Fe2+(P,Si)Si6B3O34F14 |
| 9.AJ.35 | Okanoganite-(Y) | (Na,Ca)3(Y,Ce)12Si6B2O27F14 |
| 9.AJ.35 | Hundholmenite-(Y) | (Y,REE,Ca,Na)15(Al,Fe3+)(CaxAs3+1-x)(Si,As5+)Si6B3(O,F)48 |
| 9.AJ.35 | Vicanite-(Ce) | (Ca,Ce,La,Th)15As5+(As3+0.5,Na0.5)Fe3+Si6B4O40F7 |
| 9.AJ.40 | Jadarite | LiNaSiB3O7(OH) |
Fluorescence of Minasgeraisite-(Y)
Nonfluorescent in SW or LW UV.
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 Minasgeraisite-(Y)
mindat.org URL:
https://www.mindat.org/min-2716.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Minasgeraisite-(Y)
Reference List:
Foord, E. E., Gaines, R. V., Crock, J. G., Simmons, W. B., Barbosa, C. P. Jr. (1986) Minasgeraisite, a new member of the gadolinite group from Minas Gerais, Brazil. American Mineralogist, 71 (3-4) 603-607
Demartin, F., Minaglia, A., Gramaccioli, C. M. (2001) Characterization of gadolinite-group minerals using crystallographic data only: the case of hingganite-(Y) from Cuasso al Monte, Italy. The Canadian Mineralogist, 39 (4). 1105-1114 doi:10.2113/gscanmin.39.4.1105
Bačík, Peter, Miyawaki, Ritsuro, Atencio, Daniel, Cámara, Fernando, Fridrichová, Jana (2017) Nomenclature of the gadolinite supergroup. European Journal of Mineralogy, 29 (6) 1067-1082 doi:10.1127/ejm/2017/0029-2659
Cooper, Mark A., Hawthorne, Frank C. (2018) Cation order in the crystal structure of ‘minasgeraisite-(Y)’. Mineralogical Magazine, 82 (2). doi:10.1180/minmag.2017.081.043
Vereshchagin, Oleg S., Gorelova, Liudmila A., Shagova, Anastasia K., Kasatkin, Anatoly V., Škoda, Radek, Bocharov, Vladimir N., Vlasenko, Natalia S., Vašinová Galiová, Michaela (2023) Re-investigation of ‘minasgeraisite-(Y)’ from the Jaguaraçu pegmatite, Brazil and high-temperature crystal chemistry of gadolinite-supergroup minerals. Mineralogical Magazine, 87 (3) 470-479 doi:10.1180/mgm.2023.19
Localities for Minasgeraisite-(Y)
Showing 7 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.
Brazil (FRL) | |
| Foord et al. (1986) +1 other reference |
Canada | |
| BROSSEAU-LIARD (2012) | |
Czech Republic | |
| Kadlec T.: Nové minerály ve ... |
| Novák et al. (2013) +1 other reference |
Germany | |
| Habel (2009) |
| Witzke et al. (2014) |
Hungary | |
| Zajzon et al. (2015) |
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Jaguaraçu pegmatite, Jaguaraçu, Minas Gerais, Brazil