The encyclopdia britannica; a dictionary of arts, sciences, literature and general information . .FiGi.,il—Crystal of Bournonite, Fig. 2.—^Twinned Cry$tal ?- ?. , 6f Bournonite. crystals are tyjnned, the twin^plane being a face of the prism (»?j);the angle between the faces pf this prisni. .being nearly a rightangle (86° 20), the twinning gives rise to cruciform groups (fig. 2), and when it repeated the grpup has the appearance o^acog-wheel, hence the name Rddelerz (wheel-ore) of the Kapnikminers. The, repeated twinning gives rise to twin-lamellae,which may be detected on the fracture
The encyclopdia britannica; a dictionary of arts, sciences, literature and general information . .FiGi.,il—Crystal of Bournonite, Fig. 2.—^Twinned Cry$tal ?- ?. , 6f Bournonite. crystals are tyjnned, the twin^plane being a face of the prism (»?j);the angle between the faces pf this prisni. .being nearly a rightangle (86° 20), the twinning gives rise to cruciform groups (fig. 2), and when it repeated the grpup has the appearance o^acog-wheel, hence the name Rddelerz (wheel-ore) of the Kapnikminers. The, repeated twinning gives rise to twin-lamellae,which may be detected on the fractured surfaces, even of themassive material. The mineral is opaque, and has a brilliantmetaUic lustre with .3, lead-grey colpur. The hardness is 2|, andthe specific gravity 5-8, At the original locality. Wheal Boys in the parish of Ehdellionin Cornwall, it was found associated with jamesohite, blende andchalybite. Later,, still better crystals were found iii. anotherCornish mine, namely, Herodsfoot mine near Liskeard, whichwas worked for argentiferous galena.; Fine crystals of large
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectencyclo, bookyear1910
