Just carbon ..

yea,concrete is important,but the cost of electricity is a joke..burnt coal, fly ash and lime make up cement..sun,wind and water can help with our large power bills,especially those large tidal movements.

But a big hammer can smash one.

Coal is quite incredible. When viewed closely you can see why diamonds and coal are related.

the new valued minerals now are used for mobile phones.or for brake pads on cars or lithium for batteries.

Diamond is hard, but not tough, as MobyDisc alluded to.

They are completely different properties.

Carbon is an amazing substance...

cleantechnica.com/2012/07/06/mit-researchers-use-graphene-for-energy-efficient-desalination/

I assume it was both physically and mentally tiring concreting your driveway ?

I think you may find that :

Coal isn't pure carbon and doesn't directly turn into diamonds.
Diamonds form about 50km below the earth's crust at 50 times atmospheric pressure and 2000 degrees C
It takes millions of years for blocks of carbon to turn into diamonds in these conditions
Modern man evolved about 200,000 years ago and walked out of Africa about 80,000 years ago.

So, when the coal we are currently digging at up to 60m below the earth's crust, sinks due to geological processes to 60km, then spends a couple million years turning into diamonds, then gets uplifted back to the surface to be collected, history suggest man will have either evolved into something quite different to man, or been replaced by something else.

The chance that our decedents would ever be able to obtain naturally occurring diamonds from the coal we are currently mining is just about zero.

Probably more likely they manufacture a different substance that is harder than diamond, stronger than diamond, more ductile than diamond and cheaper than diamond and place diamonds in museums to marvel at how the ancients fought trade wars over such trivial things.

Frogs kettle in goldfish