>>12909302Carbon forms into diamond from high pressures and temperatures caused by being very deep down into the Earth, at least 90 miles, and possibly from other pressure sources at the same time like continental plates colliding.
Most diamonds make their way up higher for us to get in other rocks like kimberlite via old lava vents or volcanos (when they were active).
I admit I thought it was coal until Google educated me that it is pure carbon in the mantle not old wood coal. I should of known, how the hell does old wood coal make it 90 miles down. There's a lot of un-weathered rock in the way that has persisted throughout time.
