Fine grained disseminated gold occurs within pyrite or associated with arsenopyrite and bournonite
. The broad mineralisation zones are the result of a culmination of intersecting structures beneath interpreted shallow dipping shear zone 'fault valves'.
Stage 4 is marked by a mineral assemblage composed of quartz + antimony-lead-silver sulfosalt minerals (Figure 4(r)) that prevailingly include boulangerite and jamesonite, as well as minor bournonite
, tetrahedrite, and andorite.
Also from the Mundo Nuevo district there's tetrahedrite with bournonite
, in specimens from 3 to 12 cm across which are clusters of sharp tetrahedral crystals of tetrahedrite completely coated by lustrous metallic black bournonite
, the latter as microcrystal druses which roughen, but add interest to, the tetrahedrite faces--a single flat of these specimens was with Jaroslav Hyrsl.
Locally present are stibnite and chalcopyrite, as are lesser distributions of pentlandite (Ni,FeS), arsenopyrite, boulangerite (5PbS.2[Sb.sub.2][S.sub.3]), bournonite
(2PbS.[Cu.sub.2]S.[Sb.sub.2][S.sub.3]) and cinnabar.
In the Keyue deposit, the ore minerals include sphalerite, galena, pyrite, arsenopyrite, chalcopyrite, tetrahedrite, freibergite, boulangerite, jamesonite, bournonite
, and stibnite; the gangue minerals are mainly Mn-Fe carbonate, quartz, and calcite (Figures 4-6); and the supergenesis generates the minerals that prevailingly include ferrohydrite, sardinianite, valentinite, malachite, and siliceous sinter (Figure 7).
The National Museums of Scotland set up two cases previewing future galleries, with antique classics from Leadhills plus a breathtaking Cornwall bournonite
specimen about 40 cm across.
Using an X-ray spectrometer as the main device in the mineralogical study, the effects of pulp properties (in soda or lime environment) and flotation kinetics were evaluated: gudmundite (FeSbS) is depressed in soda as well as in a lime environment; boulangerite ([Pb.sub.5][Sb.sub.4][S.sub.11]) gives better results in a soda environment; bournonite
([CuPbSbS.sub.3]) floats very well in both environments and is near to chalcopyrite in its properties.
, native antimony and argentiferous tetrahedrite are common as microscopic inclusions in galena.
A number of other minerals have been found there as well, including the rare minerals bottinoite and brianyoungite (for which the mine is the type locality), and a suite of primary minerals (bournonite
, millerite, strontianite, and ullmannite) which are not common in other Mississippi Valley-type deposits.
Also, Jaroslav Hyrsl had in his InnSuites room a flat of thumbnail specimens of bournonite
from Machacamarca, Bolivia: the luster is dull but the sharp gray bournonite
crystals reach almost 3 cm, and these thumbnails were "on special sale" for an amazing $5 to $10.
He was 27 when he loaned this bournonite
crystal to James Sowerby.