Fulgurite – Libyan desert, Egypt

A fulgurite, also called a fossilized lightning bolt or lightning bolt, is a glassy formation formed by lightning striking sand or other material containing quartz. When lightning strikes, the temperature reaches up to 30,000 °C and melts the silica particles. The lightning heats the sand so quickly that the sand melts and then cools rapidly, forming tubes, cavities or other glassy structures called fulgurites. These are systematically classified as so-called shock metamorphosed rocks.

Fulgurites can vary in length and thickness depending on the intensity and length of the flash. The colour usually ranges from clear to pink or brown to black, depending on the content of impurities in the sand.

The inner walls of fulgurites are covered with a glassy layer formed by the melting of sand. Traces of partially melted sand grains are visible on the outer surface. Fulgurites are relatively fragile and easily broken, which makes it difficult to collect larger pieces and increases their price.