Bournonite

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Bournonite
Bournonite 2.jpg
Bournonite and baryte
General
Category Sulfosalt mineral
Formula
(repeating unit)
PbCuSbS3
Strunz classification 02.GA.50
Dana classification 3.4.3.2
Identification
Color Steel-gray to iron-black
Crystal habit Crystals short prismatic to tabular, typically striated; commonly as subparallel aggregates. Also massive, granular to compact
Crystal system Orthorhombic
Twinning On {110}, commonly forming cross or cogwheel aggregates
Cleavage [010] Imperfect
Fracture Subconchoidal to uneven
Mohs scale hardness 2.5 - 3.0
Luster Brilliant to dull
Streak Steel-gray to iron-black
Diaphaneity Opaque
Specific gravity 5.7 - 5.9
Pleochroism Very weak
References [1][2]

Bournonite is a sulfosalt mineral species, a sulfantimonite of lead and copper with the formula PbCuSbS3.

It was first mentioned by Philip Rashleigh in 1797 as an ore of antimony and was more completely described in 1804 by French crystallographer and mineralogist Jacques Louis, Comte de Bournon (1751–1825), after whom it was named. The name given by Bournon himself (in 1813) was endellione, since used in the form endellionite, after the locality in Cornwall where the mineral was first found.

The crystals are orthorhombic, and are generally tabular in habit owing to the predominance of the basal pinacoid; numerous smooth bright faces are often developed on the edges and corners of the crystals. They are usually twinned, the twin-plane being a face of the prism (m); the angle between the faces of this prism being nearly a right angIe (86° 20′), the twinning gives rise to cruciform groups and when it is often repeated the group has the appearance of a cog-wheel, hence the name Rãdelerz (wheel-ore) of the Kapnik miners. The repeated twinning gives rise to twin-lamellae, which may be detected on the fractured surfaces, even of the massive material.[3]

It is a mineral in medium temperature hydrothermal vein deposits. It commonly occurs with galena, tetrahedrite, sphalerite, chalcopyrite, pyrite, stibnite, zinkenite, siderite, quartz, rhodochrosite, dolomite and barite.[1]

It was first described for an occurrence in Wheal Boys in the parish of St Endellion in Cornwall,[4] it was found associated with jamesonite, sphalerite and siderite. Later, still better crystals were found in another Cornish mine, namely, Herodsfoot mine near Liskeard, which was worked for argentiferous galena. Fine crystals of large size have been found with quartz and siderite in the mines at Neudorf in the Harz, and with sphalerite and tetrahedrite at Cavnic near Baia Mare in Romania.[3] It has been reported from a large number of other localities.[1][5]

External links[edit]

References[edit]

  1. ^ a b c http://rruff.geo.arizona.edu/doclib/hom/bournonite.pdf Handbook of Mineralogy
  2. ^ http://webmineral.com/data/Bournonite.shtml Webmineral data
  3. ^ a b Public Domain One or more of the preceding sentences incorporates text from a publication now in the public domainChisholm, Hugh, ed. (1911). "Bournonite". Encyclopædia Britannica 4 (11th ed.). Cambridge University Press. p. 333. 
  4. ^ http://www.mindat.org/min-741.html Mindat
  5. ^ http://www.mindat.org/show.php?id=741&ld=1#themap Mindat with location data