Diamonds, made of carbon atoms, are the hardest natural ... of a mineral called corundum, comprised of aluminum oxide. The red color is caused by traces of chromium. Corundum also forms sapphire ...

Iron on its own makes yellow sapphires, and can also give us green stones. Chromium turns the corundum pink or red, and that's how we get rubies. What's more, whole other minerals – such as ...

The kyawthuite crystal was discovered in 2010 by sapphire hunters ... synthetic replicas of the mineral—chemically identical and easier to produce—the natural kyawthuite crystal embodies ...