whaaaa? U talking 'bout diamonds or platinum? Diamonds are expensive because of the process necessary to make them and that is tooooooooooooooooooooooooooooooooons of pressure. basically carbon is one of the best elements there is. a carbon composite can be as tough as steel but lighter.
no no no. not charcoal. charcoal is made from wood. just coal, the coal found in mining. yes. it is as of now still impossible to produce diamonds artificially. otherwise they would be cheaper.
the actual time it takes to produce a diamond naturally takes centuries. for a machine I say it would be slowly compressing carbon rods for merely hours or minutes but I guess the machine wouldn't be able to take the strain
I retract my statement. Platinum is not the strongest metal. It's pretty flexible/soft as a pure element. I meant it is the best pure metal as it does not corrode easily even compared to alloys