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.
From a mineral consisting primarily of tetrahedrite, the ore has changed to one containing tetrahedrite with varying levels of pyrite, galena, and bournonite
, Modifying the flotation process while incorporating flexibility to deal with this variability was accomplished without loss of production.
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.
11]) gives better results in a soda environment; bournonite
, native antimony and argentiferous tetrahedrite are common as microscopic inclusions in galena.
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.
The Crown Crescent lode in the Emperor mine has yielded very minor amounts of bournonite
, pyrargyrite, proustite and polybasite.
First came three stunning new bournonite
miniatures found in September 2007 at the renowned locality called Machacamarca: clean, lustrous, satiny gray "cogwheels," each about 5 cm across, are attached at high angles to form clusters devoid of matrix or associated species.
crystals to 4 mm are seen as floaters in the galena-calcite mixture.
fr) had good bournonite
miniatures from the Mine des Malines, Gard, France.
Until recently the finest examples of bournonite
were those found at the Herodsfoot mine in England over a hundred years ago.