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Bahianite
Current inventory:  0 gems
 

Bahianite

  
Bahianite was named after Bahia State, Brazil where it was discovered.

Discovered in 1974;   IMA status: Valid (IMA approved 1978)

 

Chemistry

 

 

Chemical Formula:

Al5Sb3O14(OH)2

 

Aluminum Antimony Oxide Hydroxide

Molecular Weight:

758.16 gm

Composition:

Aluminum

17.79 %

Al

33.62 %

Al2O3

 

Antimony

48.18 %

Sb

64.00 %

Sb2O5

 

Hydrogen

0.27 %

H

2.38 %

H2O

 

Oxygen

33.76 %

O

 

 

 

 

100.00 %

 

100.00 %

= TOTAL OXIDE

 

 

Classification

   

   

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/D.27-10

Nickel-Strunz 10th Ed. 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

Related to:

n/a

Varieties:

None

Synonyms:

IMA1974-027

 

 

Crystal Data

   

   

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

As water-worn, bean-shaped pebbles, to 10 cm, with polycrystalline or radial-fibrous structure; also as curved and striated crystals, diamond-shaped or rectangular, lining pockets in the pebbles.

Twinning:

As pseudohexagonal multiple contact twins, chrysoberyllike.

 

 

Physical Properties

   

 

Cleavage:

Perfect on {100}

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

9.0; Vickers: VHN100=1605 kg/mm2

Density:

4.89 - 5.46 (g/cm3)

Luminescence:

None

Radioactivity:

Not Radioactive

 

 

Optical Properties

   

   

Color:

Colorless, Cream White, Light Brown, Violet

Transparency:

Transparent, Translucent, Opaque

Luster:

Adamantine

Refractive Index:

1.810 - 1.920  Biaxial ( - )

Birefringence:

0.110

Dispersion:

r > v

Pleochroism:

Weak

 

 

Occurances

   

   

Geological Setting:

In potholes as stream-worn pebbles and as residual concentrates above weathered volcanic rock.

Common Associations:

Quartz, Andalusite, Kyanite, Diaspore, Phenakite, Eskolaite, Cassiterite, Gold

Common Impurities:

None

Type Locality:

Pico das Almas River, Paramirim das Crioulas, Érico Cardoso (old Água Quente), Bahia, Northeast Region, Brazil

Year Discovered:

1974 (IMA approved 1978)

View mineral photos:

Bahianite Mineral Photos and Locations

 

 

More Information

   

   

 

Mindat.org
Webmineral.com

 

 


Bahianite was discovered in 1974 in Bahia State, Brazil. It is a very rare gem and very unusual mineral in that it is an aluminum antimony mixed oxide with a Moh's hardness of 9. It is very rare in facet grade crystals and even then it is translucent and usually moderately to heavily included.

The only current source of Bahianite is the type locality; the region around Pico das Almas River, about eight km southeast of the village of Paramirim das Crioulas, Érico Cardoso (old Água Quente), Bahia, Northeast Region, Brazil.
 

  
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