Fulgurites: When Lightning Strikes Sand, Magic Is Formed

The amazing crystalline structures are created in a flash.

lightning over a beach and pier

Matt_Gibson / Getty Images

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. Not every lightning strike creates a fulgurite; scientists suspect that the harder packed the earth is, the more likely it will form.

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.

In 1996, University of Florida professor Martin A. Uman's research team in Florida excavated the biggest fulgurite on record—a tremendous bolt that forked into three parts, one measuring more than 16 feet, another 14 feet, and the final one 8 feet.

To be clear, in the photo below the fulgurite would have been excavated in order to appear in this way. As Science Alert points out, photos of fulgurites "already dug up or with their surroundings eroded away make it look as though these structures are formed above the ground—which is not true."

According to the Utah Geological Survey, there are two types of fulgurites: those formed when lightning hits sand and those created from rock. Sand fulgurites come from beaches and deserts, have a more glass-like interior, and can be particularly fragile. Rock fulgurites, which are rarer, form as veins inside rocks and often need to be chiseled out of their surroundings.

Finding Fulgurites

Fulgurites have been found all over the world, although they are relatively rare. Prof. Uman said in a paper, "The world is full of them. All you have to do is go to any beach and start digging." Their unusual structure, delicate nature and origin give them some value, although not in the range of precious metals. Some sites list small fulgurites for as little as $30. The more attractive pieces or those processed into jewelry can fetch a few hundred dollars.

Although most collectors seek out fulgurite solely for its looks, some people believe the lightning stones hold magical abilities to help focus divine energy, enhance creativity, or heal various illnesses. The TV show "Supernatural" used fulgurites in a few episodes to summon gods or demons, although those uses don't appear to be part of any traditional lore.

fulgurite from Mauritanian desert

Wikimedia Commons

Perhaps not surprisingly, some people enjoy making their own fulgurites, either by sticking lightning rods in sand before thunder storms or using a high-voltage power supply in a lab. The resulting fulgurites can be even more attractive than those created naturally, although obviously safety is paramount when engaging in these activities.

View Article Sources
  1. Wright, Fred W., Jr. "Florida's Fantastic Fulgurite Find." Weatherwise, vol. 51, no. 4. Jul/Aug, 1998.