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Bahianite

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Pico das Almas River, Paramirim das Crioulas, Érico Cardoso (old Água Quente), Bahia, Brazil
© O. Dziallas

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Formula:
Al
 
5
Sb
 
3
O
 
14
(OH)
 
2
System:MonoclinicColour:Tan, cream, ...
Hardness:9
Name:For the type locality.
This page provides mineralogical data about Bahianite.

Classification of Bahianite

IMA status:Approved
Strunz 8th edition ID:4/D.27-10
Nickel-Strunz 10th (pending) edition ID: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
Dana 8th edition ID:44.3.7.1

44 : ANTIMONATES
3 : Miscellaneous
Hey's CIM Ref.:7.13.7

7 : Oxides and Hydroxides
13 : Oxides of As, Sb and Bi
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Type Occurrence of Bahianite

Type Locality:Pico das Almas River, Paramirim das Crioulas, Érico Cardoso (old Água Quente), Bahia, Brazil
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)
Year of Discovery:1978
Geological Setting of type material:In potholes as stream-worn pebbles and as residual concentrates above weathered volcanic rock

Physical Properties of Bahianite

Lustre:Adamantine
Diaphaneity (Transparency):Transparent, Translucent
Colour:Tan, cream, orange-brown, brown; crystals colourless, tan, pale violet; yellow internal reflections in transmitted light
Hardness (Mohs):9
Hardness (Vickers):VHN100=1605 kg/mm2
Cleavage:Perfect
on {100}
Fracture:Irregular/Uneven
Density (measured):4.78 - 5.46 g/cm3
Density (calculated):5.26 g/cm3

Crystallography of Bahianite

Crystal System:Monoclinic
Class (H-M):2/m - Prismatic
Space Group:B2/m {B1 1 2/m} {C2/m} {C1 2/m 1}
Cell Parameters:a = 9.406Å, b = 11.541Å, c = 4.41Å
β = 90.94°
Ratio:a:b:c = 0.815 : 1 : 0.382
Unit Cell Volume: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 Diffraction:
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

Optical Data of Bahianite

Type:Biaxial (-)
RI values: nα = 1.810 nβ = 1.870 nγ = 1.920
Maximum Birefringence:δ = 0.110

Chart 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 Bahianite

Formula:
Al
 
5
Sb
 
3
O
 
14
(OH)
 
2
Essential elements:Al, H, O, Sb
All elements listed in formula:Al, H, O, Sb
Analytical Data:Averages of four electron microprobe analyses of material from Paramirim, Bahia, Brazil; total iron calculated as Fe2O3; water determined by Penfield's method
WO3 (1.20)
Sb2O5 (57.28)
SiO2 (1.03)
Al2O3 (35.37)
Fe2O3 (1.04)
BeO (0.75)
H2O (2.77)
Empirical Formula:
Al
 
5.49
Be
 
0.24
Si
 
0.14
Fe
3+
0.10
W
 
0.04
Sb
 
2.80
O
 
14
(OH)
 
2.44

Relationship of Bahianite to other Species

Related Minerals - Nickel-Strunz Grouping):

- +
4.DC.10Simpsonite
Al
 
4
(Ta,Nb)
 
3
O
 
13
(OH,F)
Related Minerals - Hey's Index Grouping:

- +
7.13.1Arsenolite
As
 
2
O
 
3
7.13.2Claudetite
As
 
2
O
 
3
7.13.3Sénarmontite
Sb
 
2
O
 
3
7.13.4Valentinite
Sb
 
2
O
 
3
7.13.5Cervantite
Sb
3+
 
Sb
5+
 
O
 
4
7.13.6Stibiconite
7.13.8Cyanophyllite
Cu
 
5
Al
 
2
Sb
3+
3
O
 
12
(OH) · 12H
 
2
O
7.13.9Bismutostibiconite
Bi(Sb
5+
 
,Fe
3+
 
)
 
2
O
 
7
7.13.107.13.11Stibivanite
Sb
 
2
VO
 
5
7.13.12Bismite
Bi
 
2
O
 
3
7.13.13Sillénite
Bi
 
12
SiO
 
20

Other Names for Bahianite

Synonyms:
IMA1974-027
Other Languages:
German:Bahianit
Russian:Баиянит
Spanish:Bahianita

Other Information

Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Bahianite

Reference List:

- +
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 Bahianite

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    • Localities for Bahianite

    Hide Locality List
    (TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
    Brazil
     
    • Bahia
      • Érico Cardoso (old Água Quente)
        • 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]
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