Coal mining

[DarkhVorTeX]

I'm pretty sure that Diamonds are metamorphic.

Diamonds are formed in extreme heat and pressure under the crust and are shot up to the surface through holes in said crust (e.g. volcanoes). Definitely not metamorphic.

[JustasJ]

I'm pretty sure that Diamonds are metamorphic.

Diamonds are formed in extreme heat and pressure under the crust and are shot up to the surface through holes in said crust (e.g. volcanoes). Definitely not metamorphic.

Guess we'd need volcanoes then.

There are coal crystals that look like diamonds but are black that can be found in coal mines, though.

[Pacho]

If I remember correctly, mined coal needs to be baked first to remove impurities. I guess kiln firing would do it or something.