|Berkeley Pit from the air. Public Domain Photo.|
|Postcard ca. 1917. Public Domain photo.|
|Silver (Ag) wire. Width ~7 mm.|
|Sphalerite (ZnS) crystals. Maximum width ~2.6 cm.|
|Massive bornite. Width ~3.4 cm.|
|Crude, sooty black chalcocite crystals. Small covellite crystal shown below. Length (up-down) ~2 cm.|
|Photomicrograph, top of a covellite crystal composed of stacked plates. With quartz (white) and chalcocite (dark). width of crystal ~4 mm. Material "under" the C is foam.|
Specimen with massive covellite with nice pyrite crystals and minor quartz. Length ~3.7 cm.
Photomicrograph. Covellite and pyrite crystals. Width FOV ~1 cm.
Photomicrograph covellite crystals with reflecting faces with pyrite crystals. Width FOV ~1 cm.
|Small brittle fragment of massive digenite (blue-black) with a vein of brassy pyrite. Width of specimen ~1.1 cm. Collected at Leonard Mine, Butte District.|
Digenite (Cu9S5) is an interesting mineral first described from Germany in 1844 but rather uncommon in collections. It is associated with hydrothermal action and can either be primary (hypogene) or secondary. At Butte digenite is primary but in other localities it is often located near the intersection of the hypogene and supergene. It may be replaced by chalcocite in the higher supergene. As I understand it (and many times that is a stretch) digenite almost always contains some iron, and is usually not an important ore of copper. Crystals are rare and most specimens are fairly small masses showing conchoidal fractures. The specimen color is sort of a blue-black and have a metallic/submetallic luster. Digenite is fairly soft at 2.5-3.0 (Mohs). Small brittle fragment of massive digenite (blue-black) with a vein of brassy pyrite. Width of specimen ~1.1 cm. Collected at Leonard Mine, Butte District.
|Striated crystals of enargite. Width ~2 cm.|
|Colusite with quartz. Width specimen ~ 3.7 cm.|
|Photomicrograph colusite with quartz. FOV width ~1.0 cm.|
|Main Street, Winifred, Montana. Public Domain photo.|
|Milwaukee Railroad Depot, Winfred, Montana. Winifred was founded in 1913 as the terminus of the Chicago, Milwaukee, St. Paul and Pacific railroad. Photo from montanatom1950 at Flickr. |