Chapter Six: Why Gemstones Have Colors

Chapter Six — in which we learn nature's colouring secrets.

Here's a secret jewellers love: rubies and sapphires are the same stone. Both are a mineral called corundum. Pure corundum is completely colourless — the colours come from tiny "guests" that sneak into the crystal while it grows.

• A pinch of chromium → red → ruby.
• A dash of iron and titanium → blue → sapphire.
• Emeralds? That's chromium again, visiting a different mineral called beryl.

The amounts are unbelievably small — often less than 1% — like one drop of food colouring changing a whole swimming pool.

Amethyst is purple thanks to iron plus natural radiation from the rocks around it. And diamonds get blue from boron or yellow from nitrogen — single atoms deciding the colour of something that took billions of years to grow.

So every coloured gem is basically a recipe: one crystal, a pinch of the right ingredient, and a lot of patience. Nature has been mixing colours far longer than any artist. 🎨