F is for Fulgurite
A fulgurite is a hollow, glass tube formed in the ground when lightning strikes sand or soil. The 1800°C+ tempreatures of the lightning melts grains of silica or quartz and leaves behind a frozen impression of the vast electrical discharge. Because of this, fulgurites are sometimes referred to as petrified lightning. The longest one ever found was nearly 5 metres long ...
The word comes from the Latin fulgur meaning, simply, thunderbolt.
Archaeopteryx Blunderbuss Chthonic Dreadnought Entropy Fulgurite