At the southern end of the range closer
to Babbit a deposit of other ores have been discovered. The rocks,
composed mostly of gabbro, are part of the Duluth Complex. They contain
ores of copper, nickel, platinum and silver. Even though the amounts
are small the area is being studied by several mining companies
(International Nickel Co., Bear Creek Mining, and Exxon Minerals)
because the infrastructure and labor force are already in place for
mining. These photos are from similar kinds of rocks at a railroad cut
off Dunka Road. These rocks are
ophitic
augite troctolite (a form of gabbro),
olivine
gabbro, and
augite rich
pegmatite. They have a rusty iron staining (notice in the top
left photo) that is characteristic of copper and nickel deposits. It is
due to the weathering of the sulfides in the rock. The sulfides that
are present include
pyrrhotite
(iron sulfide),
pentlandite
(nickel sulfide) and
chalcopyrite
(copper sulfide). One of the gabbro exposures exhibits variably sized
anorthosite
inclusions that range
from 2 inches across to 10x15 foot blocks. The
anorthosite crystallized earlier
from a plagioclase rich magma only to be broken up, surrounded and
carried upward by later gabbroic magmas. In the lower right photo some
larger crystal faces of feldspar are visible. The large crystals of
gabbro have the same mineral composition of the very small grained rock
basalt.
