BUTTE  COPPER  ORE

 

Here’s a fascinating & colorful copper ore sample from the famous mines at Butte, Montana, USA.  Butte (pronounced “byoot”) is known as the “Richest Hill on Earth”.  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.

 


 

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