''The mining of taconite, a tough and abrasive low
Post# of 8054
to 30 percent iron) common to Minnesota and Michigan, is especially difficult because of the extreme
hardness of the ore. Because of this hardness, additional drilling, blasting, crushing, and grinding are
often required to extract the ore''
I think cwrn ore is only ca 1% silica not more than 2% from memory anyway so CWRN ore does not have this problem