BUTTE COPPER ORE
Here's a fascinating & colorful copper ore sample
from the famous mines at Butte, Montana, USA. Butte (pronounced ÒbyootÓ) is
known as the ÒRichest Hill on EarthÓ. The mineralized rocks at Butte have
produced gold, silver, copper, and other metals. The rock below is nicely
mineralized with copper sulfide and copper-iron sulfide minerals. Rocks
of the Butte Quartz Monzonite (a.k.a. Butte Pluton, Boulder Batholith,
mid-Campanian Stage, late Late Cretaceous, 76.3 million years) have been
intruded & altered by hydrothermal veins containing valuable metallic
minerals. The copper mineralization has been dated to 62-66 million years
ago, during the latest Maastrichtian Stage (latest Cretaceous) and Danian Stage
(Early Paleocene).
Locality:
unrecorded mine in the Butte Mining District, northeastern Silver Bow County,
southwestern Montana, USA.
Copper ore (10.7 cm across at its widest) from a copper mine at Butte, Montana,
USA.
Bluish mineral at top of rock = bornite (Cu5FeS4)
Purplish brown mineral near bottom of rock = tarnished chalcopyrite (CuFeS2)
Brassy gold specks throughout rock = pyrite (FeS2).
The rock itself is altered Butte Quartz Monzonite
of Late Cretaceous age.