This is a showy and rich, 3-dimensional cluster of sharp, dodecahedral bornite crystals to 1.2 cm on a bit of quartz-rich matrix. The steel-gray crystals are nicely lustrous and many of the crystal faces look partially melted, a common occurrence for Butte bornite. Butte bornite compares favorably with most worldwide localities and this is highly representative specimen of the species and famous locality. Classic, old-time material from the John Ydren Collection.