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Bahianite

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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:
For the type locality.
Currently 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.


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Classification of BahianiteHide

Approved
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
44.3.7.1

44 : ANTIMONATES
3 : Miscellaneous
7.13.7

7 : Oxides and Hydroxides
13 : Oxides of As, Sb and Bi

Physical Properties of BahianiteHide

Adamantine
Transparency:
Transparent, Translucent
Colour:
Tan, cream, orange-brown, brown; crystals colourless, tan, pale violet; yellow internal reflections in transmitted light
Hardness:
Hardness:
VHN100=1605 kg/mm2 - Vickers
Cleavage:
Perfect
on {100}
Fracture:
Irregular/Uneven
Density:
4.78 - 5.46 g/cm3 (Measured)    5.26 g/cm3 (Calculated)

Optical Data of BahianiteHide

Type:
Biaxial (-)
RI values:
nα = 1.810 nβ = 1.870 nγ = 1.920
Max Birefringence:
δ = 0.110
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Very High
Dispersion:
r > v
Pleochroism:
Weak

Chemical Properties of BahianiteHide

Formula:
Al5Sb3O14(OH)2
IMA Formula:
Al5Sb5+3O14(OH)2

Crystallography of BahianiteHide

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/m
Cell Parameters:
a = 9.406 Å, b = 11.541 Å, c = 4.41 Å
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

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
3.241 (100)
3.194 (100)
2.156 (80)
4.712 (70)
2.457 (70)
2.411 (70)
1.648 (70)
Comments:
Recorded on type material

Type Occurrence of BahianiteHide

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)
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 BahianiteHide

Other Language Names for BahianiteHide

German:Bahianit
Spanish:Bahianita

Common AssociatesHide

Associated Minerals Based on Photo Data:
Quartz2 photos of Bahianite associated with Quartz on mindat.org.
Muscovite2 photos of Bahianite associated with Muscovite on mindat.org.

Related Minerals - Nickel-Strunz GroupingHide

4.DC.10SimpsoniteAl4(Ta,Nb)3O13(OH,F)Trig. 3 : P3

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

7.13.1ArsenoliteAs2O3Iso. m3m (4/m 3 2/m) : Fd3m
7.13.2ClaudetiteAs2O3Mon. 2/m
7.13.3SenarmontiteSb2O3Iso. m3m (4/m 3 2/m) : Fd3m
7.13.4ValentiniteSb2O3Orth. mmm (2/m 2/m 2/m) : Pccn
7.13.5CervantiteSb3+Sb5+O4Orth.
7.13.6Stibiconite(Sb,O,OH) ?
7.13.8Cualstibite-1M(Cu,Al)3(OH)6[Sb5+(OH)6]Mon. 2/m : P21/b
7.13.9BismutostibiconiteBi(Sb5+,Fe3+)2O7Iso. m3m (4/m 3 2/m) : Fd3m
7.13.107.13.11StibivaniteSb2VO5Orth.
7.13.12BismiteBi2O3Mon. 2/m : P21/b
7.13.13SilléniteBi12SiO20Iso. 2 3 : I2 3

Other InformationHide

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 BahianiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Moore, P. B. and Araki, T. (1976): Bahianite, Al6Sb3O14(O,OH)2, a novel hexagonal close-packed oxide structure. Neues Jahrbuch für Mineralogie, Abhandlungen, 126, 113-125.
Moore, P. B., Barbosa, C. do P., and Gaines, R. V. (1978): Bahianite, Sb3Al5O14(OH)2, a new species. Mineralogical Magazine 42, 179-182. - American Mineralogist (1979) 64, 464 (abstract).
Cassedanne, J. P. (1985): Bahianite from Brazil. Mineralogical Record 16, 111-115.
Anthony, J. W. et al. (1997): Handbook of Mineralogy, Vol. 3, 34.

Internet Links for BahianiteHide

Localities for BahianiteHide

This 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.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for 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). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Brazil (TL)
 
  • Bahia
    • Érico Cardoso
      • Paramirim das Crioulas
Anthony, J. W. et al. (1997): Handbook of Mineralogy, Vol. 3, 33
Jeannine and Jacques Cassedanne : "Présence d'eskolaite dans les alluvions stannifères de la Chapada Diamantina (Bahia-Brésil), Bull. Mineral., 1980, 103, pp 600-602.
    • Paramirim
[MinRec 16:111]
Mineral and/or Locality  
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