Bornite, Sphalerite, Chalcopyrite & Quartz (Ydren Coll.)

Item Description

An old-time, very rich and showy, two-sided combination sulfide specimen from the famous East Colusa Mine at Butte. The John Ydren label, with a 1957 date, lists wurtzite as the primary sulfide on this piece. The 2002 Mineralogical Record Butte issue (Volume 33, No. 1) does not list wurzite for Butte, but MINDAT does reference wurtzite for Butte. Having reviewed the MINDAT Butte bornite and wurtzite photographs, we believe that the sharp and rounded crystals, some nicely lightly iridescent, are two forms of bornite. The showy spherical aggregates on the front are composed mainly of bornite, with a rich festooning of bright, brass-yellow, chalcopyrite crystals and scattered translucent, honey-brown sphalerite crystals. Quartz and much larger sphalerite crystals are apparent on the back and along one edge. This is an extremely fine combination Butte sulfide specimen. $3.50 was NOT cheap in 1957!