MINERAL OF THE MONTH
September 2008: Mohawkite
Technically “Mohawkite” is not a mineral but is a combination of copper arsenates with nickel and cobalt. It is also considered a variety of Domeykite. It is named after the original locality: the Mohawk Mine located in the Keeweenaw Peninsula of Michigan’s Upper Peninsula. This is the only location in the world that Mohawkite is found. The cubic crystals are rare in that the mineral more typically forms in masses, especially filling veins in hydrothermal vents. On a freshly fractured or mined surface, it appears whitish, but quickly tarnishes to brown. Sometimes the oxidized surface appears to have iridescence as it tarnishes. It has a hardness of between 3 and 3.5 with a specific gravity of between 7.2 and 7.9. It has a metallic luster with a brownish streak. Because of its speckled formation and combination of minerals, it has an uneven fracture. It is believed that the nickel arsenides crystallized first at higher temperatures. Later, fracturing occurred and some of the nickel was replaced by the copper arsenides-bearing solutions.
Mineral of the Month Archives
May 2007 Rainbow Fluorite
June 2007 Lake Superior Michipicoten Agate
July 2007 Labadorite
August 2007 Rain Flower Agate
Fall 2007 Malachite
December 2007 Nepheline Syenite
January 2008 Native Copper
February 2008 Amazonite
March 2008 Lake Superior Agate
April 2008 Shadow Agate
May 2008 Apohpylite
June 2008 Ocean Jasper
Summer 2008 Marra Mamba Tiger's Eye
September 2008 Mohawkite
October 2008 Mexican opal
November 2008 Prehnite
December 2008 Picture Jasper
January 2009 Sea Shell Jasper
February 2009 Polychrome Jasper
March 2009 Selenite Desert Rose
Spring 2009 Coyamito Agate
July 2009 Obsidian Needles
August 2009 Goethite
September 2009 Banded Iron Formation
Fall 2009 Fairburn Agate
February 2010 Kentucky Agate
March 2010 Fossilized Dinosaur Bone
April/May 2010 Kentucky Agate
Copyright All rights reserved.
Gitche Gumee Museum.
E21739 Brazel Street
Grand Marais, Michigan 49839
