Bahianite
Current inventory:  0 gems
 

  
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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