Question

is mining lower-grade ores the answer?
I need an understandable explanation, pleaseeeee. I need some help.

Answer 1

It's an ore that doesn't contain a very high proportion of valuable minerals. The term could also be applied to richer ores containing large amounts of undesirable impurities, arsenic for example. 

The opposite would be a high-grade ore, which contains a lot of the mineral or metal that you want to extract. 

Low-grade ores are less valuable than higher-grade ones. Also, recovery rates for low grade ores tend to be lower than for high grade ores - that is, a lower percentage of the total amount of metal in the ore is extracted successfully. 

The definition of low- and high-grade depends on the resource in question. For copper, low grade ores have less than 1% copper. For gold, an ore having 1% gold by mass would be considered (very) high-grade, as gold is more valuable than copper. As other answerers pointed out, the cutoff for iron ore is even higher, as iron is less valuable than coppe

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