- Bournonite
Bournonite is a sulfosalt
mineral species, a sulfantimonite oflead andcopper with the formula PbCuSbS3.It was first mentioned by
Philip Rashleigh in1797 as anore ofantimony , and was more completely described by thecomte de Bournon in1804 , after whom it was named; the name given by Bournon himself (in 1813) was endellione, since used in the form endellionite, after the locality inCornwall 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. Usually, however, the crystals are 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 "Rdelerz" (wheel-ore) of theKapnik miners. The repeated twinning gives rise to twin-lamellae, which may be detected on the fractured surfaces, even of the massive material.The mineral is opaque, and has a brilliant metallic lustre with a lead-grey color. The
Mohs hardness is 2.5, and thespecific gravity is 5.8.At the original locality,
Wheal Boys in the parish ofSt Endellion in Cornwall, it was found associated withjamesonite ,blende andchalybite . Later, still better crystals were found in another Cornish mine, namely,Herodsfoot mine nearLiskeard , which was worked for argentiferousgalena . Fine crystals of large size have been found withquartz and chalybite in the mines atNeudorf in theHarz , and with blende andtetrahedrite atCavnic nearBaia Mare inRomania . A few other localities are known for this mineral.References
*1911
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