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Ya according to the fringe it's the 2nd HaRdeSt substance on earth..... indeed. Not in terms on mineral abrasion hardness, mineral fracture toughness, compressive fracture or tensile fracture strength...... so who knows what they were imagining when that claim popped out.

And it can be cut with quartz abrasive and copper (or just about any other metal they had at the time) as the lapping medium because quartz and felpspar are all less than about 10% the abrasion hardness of diamond. Oh and it's the volcanic equivalent (i.e. rhyolite) it can be knapped too.......

Granite Cutting and Drilling

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Send that check to the Egyptian workers at Aswan for their help.

Archae Solenhofen