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.
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.
Fulgurites have been found all over the world, although they are relatively rare. 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 $15. 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.
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. Check out this series of fulgurite-creation experiments below:
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Fulgurite photo: Kathy Marshall/Flickr