https://www.ccohs.ca/oshanswers/occup_workplace/underground_mining.html
What does an underground (hard rock) miner do? Anyone working underground to mine hard minerals such as ore containing gold, silver, iron, copper, zinc,...
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https://www.cat.com/en_ID/products/new/equipment/underground-hard-rock.html
Caterpillar offers a range of underground hard rock mining equipment and solutions to meet your high production demands and lower your cost per ton.
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https://www.salon.com/2014/06/21/its_a_hard_rock_life_the_steep_costs_of_koch_backed_mining_in_wisconsin_partner/?utm_source=website&utm_medium=social&utm_campaign=ogshare&utm_content=og
The industry threatens to displace Native American populations along the iron belt -- and that's just the start
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