Guimarãesite
A valid IMA mineral species
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About Guimarãesite
Djalma Guimarães
Formula:
Ca2Be4Zn5(PO4)6(OH)4 · 6H2O
Colour:
brown
Lustre:
Vitreous
Hardness:
4½
Specific Gravity:
2.963 (Calculated)
Crystal System:
Monoclinic
Member of:
Name:
Named in honor of Djalma Guimarães (5 November 1894, Santa Luzia, Minas Gerais, Brazil - 10 October 1973, Belo Horizonte, Minas Gerais, Brazil), mineralogist and geochemist, in recognition of his important contributions to Brazilian mineralogy and geology. He taught at Ouro the Preto Mining School and at the Federal University of Minas Gerais.
Name Encoding
ASCII-7:
Guimaraesite
Unique Identifiers
Mindat ID:
30764
Long-form identifier:
mindat:1:1:30764:4
Similar Names
| Guimaraesite (of Gagarin & Cuomo) | A synonym of Euxenite-(Y) |
IMA Classification of Guimarãesite
Approved
IMA Formula:
Ca2Zn2+5Be4(PO4)6(OH)4·6H2O
Approval year:
2006
First published:
2007
Classification of Guimarãesite
8.DA.10
8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
A : With small (and occasionally larger) cations
8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
A : With small (and occasionally larger) cations
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 |
|---|---|---|
| Grã | 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 Guimarãesite
Vitreous
Transparency:
Transparent
Colour:
brown
Streak:
White
Hardness:
4½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
perfect cleavage on {100} and good cleavage on {010} (by analogy)
perfect cleavage on {100} and good cleavage on {010} (by analogy)
Fracture:
Irregular/Uneven
Density:
2.963 g/cm3 (Calculated)
Optical Data of Guimarãesite
Type:
Biaxial (-)
RI values:
nα = 1.596(2) nβ = 1.600(2) nγ = 1.602(2)
2V:
Measured: 55° to 75°, Calculated: 70°
Max. Birefringence:
δ = 0.006
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 (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.
Pleochroism:
Non-pleochroic
Chemistry of Guimarãesite
Mindat Formula:
Ca2Be4Zn5(PO4)6(OH)4 · 6H2O
Element Weights:
Crystallography of Guimarãesite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/b
Setting:
C2/c
Cell Parameters:
a = 15.98(1) Å, b = 11.84(2) Å, c = 6.63(1) Å
β = 95.15(15)°
β = 95.15(15)°
Ratio:
a:b:c = 1.35 : 1 : 0.56
Unit Cell V:
1,249.35 ų (Calculated from Unit Cell)
Z:
2
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 9.48 Å | (90) |
| 5.98 Å | (100) |
| 4.82 Å | (80) |
| 3.152 Å | (90) |
| 3.052 Å | (70) |
| 2.961 Å | (70) |
| 2.841 Å | (70) |
| 2.708 Å | (80) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 34 : Complex granite pegmatites |
Type Occurrence of Guimarãesite
General Appearance of Type Material:
peripheral zones (up to 0.1 mm thick) in crystals of roscherite-group minerals.
Place of Conservation of Type Material:
under the number DR591 in the Museu de Geociã ncias,
Instituto de Geociã ncias, Universidade de São Paulo, Rua do Lago, 562, 05508080, São Paulo, SP, Brazil.
Instituto de Geociã ncias, Universidade de São Paulo, Rua do Lago, 562, 05508080, São Paulo, SP, Brazil.
Geological Setting of Type Material:
late fracture-filling mineral in a phosphate-rich granite pegmatite
Associated Minerals at Type Locality:
Synonyms of Guimarãesite
Other Language Names for Guimarãesite
Relationship of Guimarãesite to other Species
Member of:
Other Members of Roscherite Group:
| Atencioite | Ca2Fe2+3Mg2Be4(PO4)6(OH)4 · 6H2O | Tric. 1 : P1 |
| Footemineite | Ca2Mn2+Mn2+2Mn2+2Be4(PO4)6(OH)4 · 6H2O | Tric. 1 : P1 |
| Greifensteinite | Ca2Fe2+5Be4(PO4)6(OH)4 · 6H2O | Mon. 2/m : B2/b |
| Okruschite | Ca2Mn2+5Be4(AsO4)6(OH)4 · 6H2O | Mon. 2/m : B2/b |
| Roscherite | Ca2Mn2+5Be4(PO4)6(OH)4 · 6H2O | Mon. 2/m : B2/m |
| Ruifrancoite | Ca2(◻,Mn)2(Fe3+,Mn,Mg)4Be4(PO4)6(OH)4(OH,H2O)2 · 4H2O | Mon. 2/m : B2/b |
| Zanazziite | Ca2Mg5Be4(PO4)6(OH)4 · 6H2O | Mon. 2/m : B2/b |
Common Associates
Associations Based on Photo Data:
| 19 photos of Guimarãesite associated with Eosphorite | Mn2+Al(PO4)(OH)2 · H2O |
| 15 photos of Guimarãesite associated with Zanazziite | Ca2Mg5Be4(PO4)6(OH)4 · 6H2O |
| 12 photos of Guimarãesite associated with Greifensteinite | Ca2Fe2+5Be4(PO4)6(OH)4 · 6H2O |
| 11 photos of Guimarãesite associated with Microcline | K(AlSi3O8) |
| 11 photos of Guimarãesite associated with Albite | Na(AlSi3O8) |
| 7 photos of Guimarãesite associated with Quartz | SiO2 |
| 4 photos of Guimarãesite associated with Muscovite | KAl2(AlSi3O10)(OH)2 |
| 2 photos of Guimarãesite associated with Schorl | NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH) |
| 1 photo of Guimarãesite associated with Moraesite | Be2(PO4)(OH) · 4H2O |
| 1 photo of Guimarãesite associated with Roscherite Group |
Related Minerals - Strunz-mindat Grouping
| 8.DA.05 | Bearsite | Be2(AsO4)(OH) · 4H2O |
| 8.DA.05 | Moraesite | Be2(PO4)(OH) · 4H2O |
| 8.DA.10 | Zanazziite | Ca2Mg5Be4(PO4)6(OH)4 · 6H2O |
| 8.DA.10 | Atencioite | Ca2Fe2+3Mg2Be4(PO4)6(OH)4 · 6H2O |
| 8.DA.10 | Footemineite | Ca2Mn2+Mn2+2Mn2+2Be4(PO4)6(OH)4 · 6H2O |
| 8.DA.10 | Greifensteinite | Ca2Fe2+5Be4(PO4)6(OH)4 · 6H2O |
| 8.DA.10 | Roscherite | Ca2Mn2+5Be4(PO4)6(OH)4 · 6H2O |
| 8.DA.10 | Ruifrancoite | Ca2(◻,Mn)2(Fe3+,Mn,Mg)4Be4(PO4)6(OH)4(OH,H2O)2 · 4H2O |
| 8.DA.10 | Okruschite | Ca2Mn2+5Be4(AsO4)6(OH)4 · 6H2O |
| 8.DA.15 | Uralolite | Ca2Be4(PO4)3(OH)3 · 5H2O |
| 8.DA.20 | Weinebeneite | CaBe3(PO4)2(OH)2 · 4H2O |
| 8.DA.25 | Tiptopite | K2(Na,Ca)2Li3Be6(PO4)6(OH)2 · H2O |
| 8.DA.40 | Spencerite | Zn4(PO4)2(OH)2 · 3H2O |
| 8.DA.45 | Glucine | CaBe4(PO4)2(OH)4 · 0.5H2O |
Fluorescence of Guimarãesite
none
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 Guimarãesite
mindat.org URL:
https://www.mindat.org/min-30764.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Guimarãesite
Localities for Guimarãesite
Showing 2 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 (TL) | |
| Chukanov et al. (2007) |
| Luis Menezes +1 other reference |
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Piauí valley, Taquaral, Itinga, Minas Gerais, Brazil