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Povondraite  (Tourmaline)
Current inventory:  0 gems
 

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.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/E.19-75

8 : Silicates
E : Cyclosilicates, triplet rings [Si3O9]6-
19 : Tourmaline group

Crystal Data

Crystallography:

Trigonal - Ditrigonal Pyramidal

Crystal Habit:

Crystals are equant but distorted prisms, terminated by trigonal pyramids, in subparallel aggregates, to several mm.

Twinning:

None

Physical Properties

Cleavage:

None

Fracture:

Uneven to Conchoidal

Tenacity:

Brittle

Moh's Hardness:

7.0 ~

Density:

3.26 (g/cm³)

Luminescence:

None

Radioactivity:

Barely detectable; GRapi = 11.91 (Gamma Ray American Petroleum Institute Units)

Optical Properties

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

Pleochroism:

Strong; O = yellow-brown, dark brown, brown-black; E = dark red-brown, light brown.

Occurances

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

More Information

Mindat.org
Webmineral.com

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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