Biwabik Iron Formation at the LTV Mine

The iron mines below have been inactive for at least 3 years at the time of the photos. Very little vegetation has established itself in the hard slate rock called taconite. The mine originally operated by erie Mining Company was the second mining operation to mine taconite in 11 different pits starting in 1957.1 I believe most of these photos are in LTV Pit  5. Notice the rock cleavage that results in parallel faces of both the rock shelf and the large samples that were too large to carry in the photos below.

slate
slate sample
mine site
mine site2
The above photos show the magnetite mineral resources at this location. The top of the "cliff" is the original ground level with the slaty layer of magnetite below. Many of the fractures of the rock have been caused by explosives to break the hard rock into pieces that can be loaded into trucks and dumped into crushers.

The photos at the right and below show the layering of the magnetite - one of two kinds of minerals that attract magnets (the other, lodestone, not only attracts magnets but is a magnet itself). Between the layers of the usable iron ore (dark gray) are the reddish layers of jasper, a red colored form of chert both of which are micro crystalline forms of the mineral quartz.

Just to the north of this location is an outcrop of Pokegama Quartzite. This rock made from metamorphosed sand is at the bottom of the iron formation. More details of this are on the next page.
slaty magnatite
 
taconite
taconite

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1.  MN DNR Minerals Education Workshop Field Trip