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That is really a very common circumstance. Some of the best Turquoise ever mined came from places like Bisbee and Kingman where copper mining was the main goal and the mine operators allowed the...

It's about the same with any economically desirable rock or mineral. Go back a couple hundred years and the pickings were plenty. You could literally walk along the surface and pick up all manner of...

If you were doing a scientific treatise on specific gravity and were trying to correlate it to hardness you would be in big trouble. Diamond has a S.G of around 3.4 or so and the main ore of lead...

I'm not sure what specific gravity has to do with hardness. Specific Gravity deals with density. Lead and Gold have high specific gravity however they are very soft materials.