Fulgurite

Branching tubes of glass formed when lightning strikes sand and melts it instantly.

Fulgurite specimen — Photo: John Alan Elson, CC BY-SA 4.0, via Wikimedia Commons

How to identify fulgurite

Hollow, root-like tubes.
Glassy, bubbly lining; rough sand-coated outside.
Fragile and light.

Often confused with

Concretion
Concretions are solid, not hollow glass tubes.
Compare side by side

Where it's found

Sahara Desert
Florida beaches
Michigan dunes

Uses

Collector specimens.

Rock tumbling

Not suitable for tumbling.

Did you know?

Lightning can heat sand above 1,800 °C in a fraction of a second.

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