The pile at the left of the
above photo (west) is overburden - the glacial till and other material
that is scraped off and piled up to provide access to the ore. In the
photo above right members of the workshop are collecting samples of ore
containing rock. One sample (right) shows the metallic gray
hematite ore in layers with jasper, a form of micro crystalline quartz.
In many places Mary-Ellen Jasper is noticeable. Mary-Ellen Jasper is
the
fossil of stromatolites, a form of blue-green algae of the late
precambrian era. These fossils are 1.8 to 2 billion years old and are
believed to be among the earliest forms of life on earth. The
stromatolites would produce oxygen in a marine environment that was
rich in ferrous (iron in the +2 oxidation state) ions. The combination
of the ferrous iron and the oxygen would cause precipitation of the
hematite minerals along with the silica (quartz). Mary-Ellen Jasper has
a hardness from 6.5 to 7 (the same as glass - quartz) with colors of
red, pink, white, yellow and even green. It occurs commonly in the
Biwabik Iron Formation forming bands of iron and chert in the Mesabi
Iron Range.
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