"Mohawkite" is not considered a mineral but is a combination of copper arsenates with Nickel and Cobalt. For an in depth analysis, this link provides some valuable information and references.
http://www.minsocam.org/msa/collectors_corner/arc/mohawkmi.htm
Mohawkite is also considered a variety of Domeykite. The following list of properties refers to Domeykite.
CHEMISTRY - Cu3As
CRYSTALLOGRAPHY - Cubic
CRYSTAL GROWTH AND HABITS - Crystals are rare and the mineral normally forms as botryoidal or reniform masses or as massive vein fillings.
COLOR AND OTHER OPTICAL PROPERTIES - On a fresh surface Mohawkite/Domeykite appears tin white to yellowish white but quickly tarnishes to brown. It often develops an iridescence as the tarnishing develops.
HARDNESS - 3 - 3.5
SPECIFIC GRAVITY - 7.2 - 7.9
LUSTER - Metallic
STREAK - Brownish
BREAKABILITY - Uneven fracture
OCCURRENCE - Hydrothermal
ASSOCIATED MINERALS - Copper, silver
MINERAL NAMES - Mohawkite is derived from the Mohawk Mine in Michigan and Domeykite is named after the Chilean mineralogist Ignacio Domeyko.