Valentinite

Valentinite

A sample of valentinite from Algeria (size: 6.9 x 4.4 x 3.3 cm)
General
Category Oxide minerals
Formula
(repeating unit)		 Sb2O3
Strunz classification 4.CB.55
Crystal system Orthorhombic
Crystal class Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space group Pccn
Unit cell a = 4.91 Å, b = 12.46 Å
c = 5.42 Å; Z = 4
Identification
Color Colorless, snow-white, pale yellow, pink, gray to brownish
Crystal habit Prismatic crystals, sometimes flattened, fan-shaped or stellate aggregates of crystals; lamellar, columnar, granular, massive.
Cleavage {110}, perfect; {010}, imperfect
Tenacity Brittle
Mohs scale hardness 2.5–3
Luster Adamantine, pearly on cleavages
Streak White
Diaphaneity Transparent to translucent
Specific gravity 5.76
Optical properties Biaxial (-)
Refractive index nα = 2.180 nβ = 2.350 nγ = 2.350
Birefringence δ = 0.170
2V angle Very small
References [1][2][3]

Valentinite is an antimony oxide mineral with formula Sb2O3. Valentinite crystallizes in the orthorhombic system and typically forms as radiating clusters of euhedral crystals or as fibrous masses. It is colorless to white with occasional shades or tints of yellow and red. It has a Mohs hardness of 2.5 to 3 and a specific gravity of 5.76.[4] Valentinite occurs as a weathering product of stibnite and other antimony minerals. It is dimorphous with the isometric antimony oxide senarmontite.[1]

Valetinite with pyrite from the San José Mine, Oruro City, Bolivia (size: 3.9 x 2.8 x 1.5 cm)

Historical data

A mineral named in the middle of the 19th century in honour of Basilius Valentinus, a writer on alchemy. He is the supposed author of the first book to give a detailed description of antimony and its compounds. From the contents of the book it is also obvious that Valentinus was familiar with the synthetic preparation of antimony trioxide, which was called 'the antimony flower'.

Valentinite was first described in 1845 for an occurrence in the Les Chalanches Mine, Allemont, Isère, Rhône-Alpes, France.[2] The first description of its occurrence in the region of Pribram in Bohemia comes roughly from the same time. This particular locality at one time produced the very best crystals of this mineral. The largest crystals found there measured up to 3 cm. Grouped in rich druses, they developed in vein cavities with galena.

Occurrence

Valentinite is a weathering product of hydrothermal antimony-bearing veins, where it forms as a secondary mineral through oxidation in the upper parts of the deposits. It occurs associated with stibnite, native antimony, stibiconite, cervantite, kermesite and tetrahedrite.[1]

A rich deposit of valentinite has been found in the Constantine province of Algeria. This is the only deposit where it is mined as an ore, with 83% antimony. In all other locations it occurs in negligible quantities.

See also

References

  1. 1 2 3 Handbook of Mineralogy
  2. 1 2 Mindat with location data
  3. ↑ Webmineral data
  4. ↑ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
This article is issued from Wikipedia - version of the 10/19/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.