Keweenawite is a discredited mineral species. It was described as an
arsenide
In chemistry, an arsenide is a compound of arsenic with a less electronegative element or elements. Many metals form binary compounds containing arsenic, and these are called arsenides. They exist with many stoichiometries, and in this respect ars ...
of
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
,
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
, and
cobalt
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...
containing 39% to 54% copper, 9.7% to 20% nickel, and 0.9% cobalt.
[World Mines Register, Volumes 4-5]
/ref> Keweenawite was discovered in July 1901, in the Mohawk Mine
The Mohawk Mining Company was a major copper mining company, based in the Keweenaw Peninsula of Michigan, that was established in November 1898 and lasted until 1932. The company, between 1906 and 1932, paid out more than $15 million in shareho ...
, Keweenaw County
Keweenaw County (, ; , ) is a county in the Upper Peninsula of the U.S. state of Michigan, the state's northernmost county. As of the 2020 United States Census, the population was 2,046, making it Michigan's least populous county. It is also the ...
, Michigan
Michigan () is a state in the Great Lakes region of the upper Midwestern United States. With a population of nearly 10.12 million and an area of nearly , Michigan is the 10th-largest state by population, the 11th-largest by area, and the ...
. George A Koenig analyzed and named the copper ore.[World Mines Register, Volume 2]
/ref>
History
Keweenawite was first discovered, in July 1901, located on the fifth level of the Mohawk Mine
The Mohawk Mining Company was a major copper mining company, based in the Keweenaw Peninsula of Michigan, that was established in November 1898 and lasted until 1932. The company, between 1906 and 1932, paid out more than $15 million in shareho ...
between Shaft No. 1 and Shaft No. 2. Fred Smith, mine superintendent, sent specimens to George A Koenig for analysis. Dr. Koenig deemed it to be a new mineral species and named it Keweenawite, after its discovery locality, Keweenaw County. [The American journal of science, Volume 164]
/ref>
However, a re-analysis of the material in 1971 found the keweenite to be a mixture of the copper and nickel arsenates: α-domeykite, niccolite
Nickeline or niccolite is a mineral consisting primarily of nickel arsenide (NiAs). The naturally-occurring mineral contains roughly 43.9% nickel and 56.1% arsenic by mass, but composition of the mineral may vary slightly.
Small quantities of s ...
and rammelsbergite
Rammelsbergite is a nickel arsenide mineral with formula NiAs2. It forms metallic silvery to tin white to reddish orthorhombic prismatic crystals, and is usually massive in form. It has a Mohs hardness of 5.5 and a specific gravity of 7.1.
It was ...
.[Moore, Paul B.; ''Copper-Nickel Arsenides of the Mohawk No. 2 Mine, Mohawk, Keweenaw Co., Michigan,'' American Mineralogist, V. 56, July-August, 197]
PDF
/ref>
See also
*Mohawkite
Mohawkite is a rare rock consisting of mixtures of arsenic , silver, nickel, skutterudite and copper, with the formula Cu3As up to Cu6As, and the most desirable material was usually found in white quartz matrix. It has a hardness of 3-3.5 and a ...
- Another discredited mineral species discovered in the Mohawk mine and analysed by George A Koenig
References
Minerals
Rocks
Geology of Michigan
Keweenaw County, Michigan
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