Diamonds, made of carbon atoms, are the hardest natural substance ... showcase a ruby from Tanzania in its unpolished beauty. Rubies, valued as precious gems, are the mineral corundum in its ...

In fact, when it comes to toughness, nephrite jade is the toughest known natural mineral, tougher even than ... growing jewellery-quality gems from a “ruby seed”, and even creating glow ...

The world's rarest gemstone is made of kyawthuite, a transparent reddish-orange mineral that’s known from just one sample ...