All it takes is a flash. Lightning strikes the ground, creating temperatures of more than 3,000 degrees. The sand around the lightning strike fuses together, and fulgurite is formed. What are fulgurites? The word – based on the Latin world for thunderbolt – refers to a hollow glass tube formed when lightning strikes soil, silica, sand or even rock. These amazing structures – sometimes referred to as “petrified lightning” or “lightning stones” – don’t look like the transparent glass in your windows or kitchen cabinets. Instead they are complex structures that resemble a cross between a vegetable root and some of the more crystalline minerals such as mica. They vary in shape and size – most are only a few inches long – and they tend to form around the path of the dispersing electric charge of the lightning.