Colusite

A slight pink iridescent hue can be seen on the black mass at the top of this mostly quartz specimen.  Under the microscope, many well-formed, <1mm crystals can be observed. Colusite is a rare vanadium-tin sulfide and Butte is the type locaity. Though it carries tin, the mineral was mined for its copper content.

"Small amounts of tin in ores shipped from the Leonard, West Colusa, Mountain View and Tramway Mines of the Anaconda Copper Mining Company at Butte, Montana, have been noted for a number of years. The tin-bearing mineral was provisionally named “colusite” by Mr. Reno H. Sales, Chief Geologist of the Anaconda Company. The mineral was first noted on the 1200 foot level of the Leonard Mine near the west end of the Piccolo claim, south of the Colusa claim. The latter was one of the earliest locations in the district, and therefore it seemed appropriate to name the new mineral “colusite.”"

"Colusite, a new mineral of the sphalerite group" by Robert E. Landon; A. H. Mogilnor - Read: https://pubs.geoscienceworld.org/msa/ammin/article-abstract/18/12/528/536743/Colusite-a-new-mineral-of-the-sphalerite-group?redirectedFrom=fulltext