Note on the Occurrence of Bismutite in the Transvaal

Extract

This mineral occurs plentifully, though finely disseminated, in the veins of auriferous quartz in the Lydenburg district of the Transvaal. These veins are often capped by a "gossan" of brown hvematite, crystalline, amorphous, or at times pseudomorphous after iron pyrites; a good deal of similar brown hæmatite occurs also throughout the veins themselves. The Bismutite is disseminated irregularly through the veins, and also occurs in small pockets in the ferruginous gossan; it is from the latter source that the mineral was obtained for the subjoined description and analysis.

It is amorphous, pulverulent; colour greenish yellow to lemon-yellow, more rarely brownish yellow; opaque (feebly translucent, with waxy lustre under the microscope); its hardness appears to be about 8, but cannot well be determined on account of its pulverulent character. Specific gravity 6.86.