The town of Butte, Montana (pronounced “byoot”) is known as the “Richest Hill on Earth” and "The Mining City". The Butte Mining District has produced gold, silver, copper, molybdenum, manganese, and other metals.
The area's bedrock consists of the Butte Quartz Monzonite (a.k.a. Butte Pluton), which is part of the Boulder Batholith. The Butte Quartz Monzonite ("BQM") formed 76.3 million years ago, during the mid-Campanian Stage in the Late Cretaceous. BQM rocks have been intruded and altered by hydrothermal veins containing valuable metallic minerals - principally sulfides. The copper mineralization has been dated to 62-66 million years ago, during the latest Maastrichtian Stage (latest Cretaceous) and Danian Stage (Early Paleocene). In the supergene enrichment zone of the area, the original sulfide mineralogy has been altered.
This is the Orphan Girl Mine, on the western side of Montana Tech campus in Butte. The site is now a museum and includes the original headframe of the Orphan Girl Mine, so named because it was so far away from other Butte mines - it was alone. The mine operated from 1875 to 1957. It was a zinc-lead-silver mine, but principally a zinc mine.
The photo shows the ceiling of a decline that leads to the 65 feet level. The rock bolts are used to secure potentially loose rocks. This site was used for training by Montana Tech, hence the abundance of rock bolts - this was before the training program ran out of money.
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Info. from onsite-signage:
ORPHAN GIRL MINE
From the time it was located in 1875 until it was purchased by Marcus Daly and associates in 1879, ownership and fractional shares in the Orphan Girl Mine changed hands faster than the ante in a poker game. The Orphan Girl eventually operated to a depth of over 3,000 feet. While not a huge producer according to Butte standards, by 1944 hardrock miners had removed a respectable 7,626,540 ounces of silver as well as lead and zinc from her depths. Cool temperatures between 55 and 65 degrees made the Orphan Girl - affectionately nicknamed "Orphan Annie" or "the Girl" - a desirable place to work, unlike some "hot boxes" where temperatures could top 100 degrees. By the end of the 1920s, the Anaconda Company owned the Girl which operated until the 1950s. In 1965, the Girl became the site of the World Museum of Mining.
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Locality: Orphan Girl Mine, Butte Mining District, northeastern Silver Bow County, southwestern Montana, USA
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