Bahianite
A valid IMA mineral species
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About Bahianite
Flag of Bahia, Brazil
Formula:
Al5Sb3O14(OH)2
Colour:
Tan, cream, orange-brown, brown; crystals colourless, tan, pale violet; yellow internal reflections in transmitted light
Lustre:
Adamantine
Hardness:
9
Specific Gravity:
4.78 - 5.46
Crystal System:
Monoclinic
Name:
The name refers to the State of Bahia, Brazil, from within which state the initial specimens were found.
At the time of approval it was the only known purely aluminium antimonate mineral. Structurally related to simpsonite.
The structure is unique and is based on hcp (hexagonal close packed) arrange of oxygen atoms, the set being parallel to {001}. There are layers consisting of edge-sharing Al5O14(OH)2 sheets, that corner-link to linear trimers of the Sb3O1413- composition.
The structure is unique and is based on hcp (hexagonal close packed) arrange of oxygen atoms, the set being parallel to {001}. There are layers consisting of edge-sharing Al5O14(OH)2 sheets, that corner-link to linear trimers of the Sb3O1413- composition.
Unique Identifiers
Mindat ID:
484
Long-form identifier:
mindat:1:1:484:4
Similar Names
| Bahiaite | A rock subtype |
IMA Classification of Bahianite
Classification of Bahianite
4.DC.05
4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
C : With medium-sized cations; sheets of edge-sharing octahedra
4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
C : With medium-sized cations; sheets of edge-sharing octahedra
44.3.7.1
44 : ANTIMONATES
3 : Miscellaneous
44 : ANTIMONATES
3 : Miscellaneous
7.13.7
7 : Oxides and Hydroxides
13 : Oxides of As, Sb and Bi
7 : Oxides and Hydroxides
13 : Oxides of As, Sb and Bi
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 |
|---|---|---|
| Bhi | 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 Bahianite
Adamantine
Transparency:
Transparent, Translucent
Colour:
Tan, cream, orange-brown, brown; crystals colourless, tan, pale violet; yellow internal reflections in transmitted light
Hardness:
9 on Mohs scale
Hardness:
VHN100=1605 kg/mm2 - Vickers
Cleavage:
Perfect
on {100}
on {100}
Fracture:
Irregular/Uneven
Density:
4.78 - 5.46 g/cm3 (Measured) 5.26 g/cm3 (Calculated)
Optical Data of Bahianite
Type:
Biaxial (-)
RI values:
nα = 1.81 nβ = 1.87 nγ = 1.92
Max. Birefringence:
δ = 0.110
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.
No measured or calculated 2V is on file for this mineral, so the value used here (82°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
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.
No measured or calculated 2V is on file for this mineral, so the value used here (82°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Dispersion:
r > v
Pleochroism:
Weak
Chemistry of Bahianite
Mindat Formula:
Al5Sb3O14(OH)2
Element Weights:
Elements listed:
Crystallography of Bahianite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/m
Setting:
C2/m
Cell Parameters:
a = 9.406 Å, b = 11.541 Å, c = 4.41 Å
β = 90.94°
β = 90.94°
Ratio:
a:b:c = 0.815 : 1 : 0.382
Unit Cell V:
478.66 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Curved and striated crystals, diamond-shaped or rectangular
Twinning:
Pseudohexagonal multiple contact twins, chrysoberyl-like
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
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Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
Remove metal-metal sticks
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2D | Stereo | Red-Blue | Red-Cyan
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View
CIF File Best | x | y | z | a | b | c
CIF File Best | x | y | z | a | b | c
Rotation
Stop | Start
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Labels
Console Off | On | Grey | Yellow
Console Off | On | Grey | Yellow
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) |
|---|---|---|---|---|---|---|---|
| 0014703 | Bahianite | Moore P B, Araki T (1976) Bahianite, Al5Sb3O14(O,OH)2, a novel hexagonal close-packed oxide structure Neues Jahrbuch fur Mineralogie, Abhandlungen 126 113-125 | 1976 | Serra de Mangabeira, Bahia, Brazil | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.241 Å | (100) |
| 3.194 Å | (100) |
| 2.156 Å | (80) |
| 4.712 Å | (70) |
| 2.457 Å | (70) |
| 2.411 Å | (70) |
| 1.648 Å | (70) |
Comments:
Recorded on type material
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 26 : Hadean detrital minerals | |
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47d : [Arsenates, antimonates, selenates, bismuthinates] |
Type Occurrence of Bahianite
General Appearance of Type Material:
Water-worn, bean-shaped pebbles, to 10 cm, with polycrystalline or radial-fibrous structure; also as crystals, lining pockets in the pebbles
Place of Conservation of Type Material:
Harvard University, Cambridge, Massachusetts, USA (No. 119088);
National Museum of Natural History, Washington, D.C., USA (Nos. 133875, 135922)
National Museum of Natural History, Washington, D.C., USA (Nos. 133875, 135922)
Geological Setting of Type Material:
In potholes as stream-worn pebbles and as residual concentrates above weathered volcanic rock
Associated Minerals at Type Locality:
Synonyms of Bahianite
Other Language Names for Bahianite
Common Associates
Associations Based on Photo Data:
Related Minerals - Strunz-mindat Grouping
| 4.DC.10 | Simpsonite | Al4Ta3O13(OH) |
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 Bahianite
mindat.org URL:
https://www.mindat.org/min-484.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Bahianite
Reference List:
Moore, Paul B., Carlos do Prado Barbosa, , Gaines, Richard V. (1978) Bahianite, Sb3Al5O14(OH)2, a new species. Mineralogical Magazine, 42 (322) 179-182 doi:10.1180/minmag.1978.042.322.02
Localities for Bahianite
Showing 3 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 | |
| Cassedanne et al. (1980) |
| Anthony (1997) |
| Cassedanne (1985) |
Quick NavTopAbout BahianiteUnique IdentifiersSimilar NamesIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesCommon AssociatesStrunz-MindatOther InformationInternet Links References Localities Locality List
Pico das Almas river, Paramirim das Crioulas, Érico Cardoso, Bahia, Brazil