Hard rock mining, mining of metals and other hard minerals.

Next to emery, jade was the hardest mineral known to ancient Mesoamerica.

Wet grinding of hard minerals is usually much more efficient than dry grinding.

As it says in Mohs scale, the diamond is always at the most top of the scale, being the hardest mineral.

The iron pikes we carried were ill-adapted to digging out the hard, glowing mineral.

A jewel in a mechanical watch is a small, shaped piece of a hard mineral.

These trees are then called petrified because the hard minerals have replaced the tissues of the long dead tree.

Assuming it is very hard mineral, though, we estimate that the object when it hits will be at least a hundred or more meters across.

Diamond: the hardest mineral, another form of carbon.

Then they're recorded by hydrophones and a tracing is made showing where there might be hard minerals below the bottom surface.