Question: whats the hardest rock in the world

Tiernan answered on 6 Nov 2018:

Well, igneous rocks are pretty tough because they form from magma that cools so they tend to be really tightly stuck together. Migmatite – which is like granite – is really tough, and it’s really hard to dig or drill it out. Diamonds are the hardest mineral and are pure carbon they has been really pressurised 10s of kilometres beneath the surface. Graphite is also pure carbon, so chemically it’s exactly the same as diamond, but it forms nearer the surface and it really soft. Same chemistry, different environments leads to completely different minerals with completely different strengths