Was the Trojan War Fought Over a Rock?

According to legend, Helen of Troy was so beautiful that her face launched a thousand ships, leading to the Trojan War  more than 3000 years ago.

But other stories suggest that  it might not have been her face, but her jewelry that was  the key to her desirability.

She was said to possess a rare and magical stone that shone like a star.

While this might seem like a tall tale that got distorted over the millennia, the existence of starry gemstones is no myth.

Star sapphires and star rubies  really do reflect six pointed stars.

And they owe that trick not to their purity, but to some tiny imperfections  in an otherwise common mineral.

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As gemstones go, Corundum is pretty easy to find. It’s made from aluminum and oxygen  that combines to make hexagonal or double-pyramid-shaped crystals,  and it exists all over the planet.

But the thing about this aluminum oxide structure is that it’s incredible hard.

In fact corundum is the second  hardest natural substance we know of, second only to diamond.

It crystallizes from slow-cooling  igneous and metamorphic rocks, in places that are rich in aluminum, but have no silica.

And because it’s so hard, it readily survives erosion and weathering.