Lightning strikes the ground at a temperature five times hotter than the sun, sometimes fusing the earth it hits into stone or glass known as fulgurite — also called fossilized or petrified lightning.

Pronounced FUL-gyuh-right, the word comes from the Latin word "fulgur," meaning lightning. The word was first used in 1823, but ancient Roman philosophers talked about the phenomenon more than 2,000 years ago.

These rocks form from the intense heat of a lightning strike, which instantly vaporizes water in the ground — and sometimes the ground itself. That heat melts the surrounding sand into a molten material, which then expands before cooling and solidifying into a tube of glass and rock.

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They often resemble tree roots or rocky straws with smooth interiors and bumpier exteriors.

The tubes can be very long depending on how far lightning travels from its point of contact with the ground. Some tubes can be as long as 5 feet.

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Fulgurite rocks tend to be narrow – often less than one inch wide with a hollow, glassy center.

How to get some

If you find yourself in a thunderstorm near the beach, you might be able to find pieces of fulgurite after the storm moves away. That last part is important.

If you see lightning strike a beach, wait at least half an hour after you hear the last rumble of thunder, then head outside and see if you can find any harder clumps of sand.

Fulgurite isn't likely to be hot or electrically charged, so it is safe to touch, but many of these rocks are quite delicate. The fragile rocks should be removed from the sand with care.

You can find fulgurite in any sandy areas, such as salt flats or deserts, and sometimes on mountains.