Mohawkite is a rare rock consisting of mixtures of the elements
arsenic,
silver,
nickel and
copper, and the mineral
skutterudite, with the chemical formula Cu
3As up to Cu
6As, and the most desirable material was usually found in white
quartz matrix. Named after the
Mohawk Mine in the
Keweenaw Peninsula of the U.S. state of
Michigan, where it was originally found, mohawkite has a hardness on the
Mohs scale of 3.0 to 3.5 and a metallic luster. The rock's color ranges from brassy yellow to metallic gray, with some specimens having a blue or greenish surface tarnish. This nugget of mohawkite measures about 50 mm × 40 mm × 28 mm (2.0 in × 1.6 in × 1.1 in).
Photograph credit: Heinrich Pniok