Cliff mine
Encyclopedia
The Cliff mine was the first successful copper mine in the Copper Country
of the state of Michigan
in the United States
. The mine is at the now-abandoned town of Clifton
in Keweenaw County
. Mining began in 1845, and the Cliff was the most productive copper mine in the United States from 1845 through 1854. Large-scale mining stopped in 1878.
The Cliff mined a fissure vein of native copper
in Precambrian
conglomerate and basalt
beds. The vein was nearly vertical, dipping steeply to the east, and running north-south, nearly perpendicular to the strike of the enclosing beds. The productive part of the vein was below the Greenstone flow, which forms the cliff from which the mine took its name. The mine started by mining only high-grade ore; in 1848, the average grade mined was 26% copper. The average ore grade mined declined over time, and by 1869 was 3% copper, comparable to other copper mines of the time. Some native silver was also recovered; approximately 41,000 ounces total silver was reported recovered in the years 1846-1852 and 1858-1871.
The Pittsburgh and Boston Copper Harbor Mining Company and its successor the Pittsburgh and Boston Mining Company operated the Cliff mine from 1845 to 1870, then sold the property to the Cliff Copper Company in 1871. The Cliff Copper Company operated the mine from 1872 to 1878. The combined dividends paid by the companies was $2.5 million. The mine was then leased to tributers, who continued minor copper production through 1887. Total production was 38.2 million pounds of refined copper.
The Tamarack Mining Company bought the Cliff property and did extensive subsurface exploration from 1903 to 1908, but did not find any new ore bodies worth mining.
During May and June of 2010, the Cliff Mine site will be the focus of Michigan Technological University
's annual Industrial Heritage and Archaeology Field School. More information about this historic mine can be found on the project website listed in the External Links section below.
Copper Country
The Copper Country is an area in the Upper Peninsula of Michigan in the United States, including all of Keweenaw County, Michigan and most of Houghton, Baraga and Ontonagon counties. The area is so named as copper mining was prevalent there from 1845 until the late 1960s, with one mine ...
of the state of Michigan
Michigan
Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. The mine is at the now-abandoned town of Clifton
Clifton, Michigan
Clifton was a community in Allouez Township, Keweenaw County, Michigan, that was founded in support of the Cliff mine—a mine opened in 1845 by the Pittsburgh and Boston Mining Company after copper was discovered there. It is located between Calumet and Eagle Harbor, off of Cliff Drive, alongside US...
in Keweenaw County
Keweenaw County, Michigan
-Demographics:As of the census of 2000, there were 2,301 people, 998 households, and 604 families residing in the county. The population density was 4 people per square mile . There were 2,327 housing units at an average density of 4 per square mile...
. Mining began in 1845, and the Cliff was the most productive copper mine in the United States from 1845 through 1854. Large-scale mining stopped in 1878.
The Cliff mined a fissure vein of native copper
Native copper
Copper, as native copper, is one of the few metallic elements to occur in uncombined form as a natural mineral, although most commonly occurs in oxidized states and mixed with other elements...
in Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
conglomerate and basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
beds. The vein was nearly vertical, dipping steeply to the east, and running north-south, nearly perpendicular to the strike of the enclosing beds. The productive part of the vein was below the Greenstone flow, which forms the cliff from which the mine took its name. The mine started by mining only high-grade ore; in 1848, the average grade mined was 26% copper. The average ore grade mined declined over time, and by 1869 was 3% copper, comparable to other copper mines of the time. Some native silver was also recovered; approximately 41,000 ounces total silver was reported recovered in the years 1846-1852 and 1858-1871.
The Pittsburgh and Boston Copper Harbor Mining Company and its successor the Pittsburgh and Boston Mining Company operated the Cliff mine from 1845 to 1870, then sold the property to the Cliff Copper Company in 1871. The Cliff Copper Company operated the mine from 1872 to 1878. The combined dividends paid by the companies was $2.5 million. The mine was then leased to tributers, who continued minor copper production through 1887. Total production was 38.2 million pounds of refined copper.
The Tamarack Mining Company bought the Cliff property and did extensive subsurface exploration from 1903 to 1908, but did not find any new ore bodies worth mining.
During May and June of 2010, the Cliff Mine site will be the focus of Michigan Technological University
Michigan Technological University
Michigan Technological University is a public research university located in Houghton, Michigan, United States. Its main campus sits on on a bluff overlooking Portage Lake...
's annual Industrial Heritage and Archaeology Field School. More information about this historic mine can be found on the project website listed in the External Links section below.
See also
- Copper mining in MichiganCopper mining in MichiganWhile it originated thousands of years earlier, copper mining in Michigan became an important industry in the 19th and early 20th centuries. Its rise marked the start of copper mining as a major industry in the United States.-Geology:...
- List of Copper Country mines
- List of Copper Country mills
External links
- Mindat.org, Cliff mine, Phoenix, Keweenaw Co., Michigan, USA, accessed 6 July 2009.
- Cliff Mine Archaeology Survey, official website and blog, CliffMine.wordpress.com, accessed 18 April 2010.