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| Chemistry:
NaFe33+Fe63+(BO3)3Si6O18(O,
OH)4 | Discovered
in 1978;
IMA
status: Valid (Approved 1993). Povondraite is named
after Dr. Pavel Povondra (1924 - ), mineralogist at
Charles University, Prague, Czech Republic, in recognition
of his work on the chemistry of the Tourmaline group. |
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Classification
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Mineral
Classification: |
Silicates |
Strunz 8th
Ed. ID:
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8/E.19-75 |
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8 : Silicates E : Cyclosilicates, triplet rings
[Si3O9]6- 19 : Tourmaline group
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Crystal
Data
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Crystallography:
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Trigonal
- Ditrigonal Pyramidal |
Crystal
Habit:
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Crystals
are equant
but distorted prisms, terminated by trigonal pyramids,
in subparallel aggregates, to several mm.
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Twinning:
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None
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Physical
Properties
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Cleavage: |
None
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Fracture: |
Uneven
to Conchoidal
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Tenacity:
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Brittle
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Moh's
Hardness: |
7.0
~
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Density:
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3.26 (g/cm3) |
Luminescence:
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None |
Radioactivity:
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Barely
detectable; GRapi = 11.91 (Gamma Ray American Petroleum Institute Units)
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Optical
Properties
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Color: |
Dark brown to brownish black,
Black |
Transparency: |
Translucent
to nearly opaque |
Luster: |
Resinous |
Refractive
Index: |
1.751 - 1.820 Uniaxial
( - ) |
Birefringence: |
0.069 |
Dispersion: |
n/a
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Pleochroism: |
Strong;
O = yellow-brown, dark brown, brown-black; E
= dark red-brown, light brown.
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Occurances
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Geological
Setting: |
Very
rare, in fractures and lining cavities in schist metamorphosed
from sedimentary rocks. |
Type
Locality: |
Alto Chapare District, Chapare Province, Cochabamba
Department, Bolivia |
Year
Discovered: |
1978 |
View
mineral photos: |
Povondraite
Mineral Photos and Locations |
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More
Information
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Mindat.org Webmineral.com |
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Povondraite
is an extremely rare member of the Tourmaline
group of minerals that was discovered in 1987. It is a gem for
collectors only since it is not particularly attractive
as it is dark brown to black and usually only translucent
to nearly opaque. Until a
recent find in Tanzania, the only known source of gem
quality crystals was the
San Francisco mine, near Villa Tunari, Alto Chapare,
Cochabamba, Bolivia where it was discovered. Povondraite
was originally called Ferridravite for its ferric iron
content and similarity to dravite color, but was redefined
and renamed upon its IMA approval in 1993.
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Povondraite
gems for sale:
We
have not photographed the Povondraite gems yet. Please check
back soon.
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