-  petrified  lightning -

or

- fulgurites -

Rare gems result from a lightning strike on sand, they form when the high temperature of the strike melts the mostly-quartzite sand and turns it into silica glass.

Mother Nature makes glass each time a large amount of energy is released during a sufficient period of time at the Earth's surface, provided that the soil composition is suitable for making glass. The latter condition is satisfied, for example, by sandy soil, with the resultant natural glass being silica glass.

There are two phenomena that are responsible for making natural glass on Earth: meteorites and lightning. Glass that is made as a result of the collision of a meteorite with the Earth's surface is called meteoritic glass or tektite. Glass (a glassy object, to be exact) that is made as a result of a cloud-to-ground lightning discharge is called a fulgurite (from the Latin "fulgur" which means lightning).

Fulgurites come in a great variety of forms and can be viewed as nature's own works of art .On average, about 100 lightning discharges occur every second on the Earth. Only about one-third of them involve ground (others occur in the clouds, between clouds, or between cloud and clear air) and potentially can make fulgurites. The peak temperature of lightning channel is of the order of 30,000° K, which is five times higher than the surface temperature of the Sun.The lightning peak temperature is considerably higher than silica's melting point which is somewhere between 1600 and 2000° C depending on moisture content.

Petrified Lightning

By SUZAN BELLINCAMPI

Some say that diamonds are a girl's best friend, but I am not pining away for those sparkly pieces of glass. There is another type of glass that I crave -- one that will not be found adorning anyone's finger, wrist or neck.

True, the object of my desire is a glass of sorts, but it can be found only at the beach or in the desert, not in a diamond mine. The jewels that I seek are petrified lightning.

Most of us have probably never heard of petrified lightning -- it doesn't even sound possible for it to exist. Even when I held a piece in my hand, I didn't believe it. But, yes, Virginia, there are fulgurites.

Fulgurites are the scientific name for petrified lightning, coming from the Latin word, fulgur, which means lightning. These rare gems result from a lightning strike on sand, and they form when the high temperature of the strike melts the mostly-quartzite sand and turns it into silica glass.

The peak temperature of a lightning channel is 30,000 degrees Kelvin, or 53,540 degrees Fahrenheit -- five times as hot as the surface of the sun. And the melting point of silica is about 3,632 degrees Fahrenheit. So, yes, Virginia, lightning can melt sand. Or, put differently, fulgurites happen.

Looking at one, you would never suspect its identity. They appear as hard, hollow tubes coated on the outside with sand. The most common colors are tan, black or brown, but they also can be translucent or white. If you are lucky enough to see one (there is one at the Boston Museum of Science), it most likely would be small, the diameter of a drinking straw, and only an inch or two long. This belies their original form.

After lightning strikes the beach (or desert), it shoots down into the sand and forms a fulgurite. The resulting structure resembles an underground tree, with a vertical trunk and horizontal branches that are surprisingly extensive. The largest fulgurite on record was found in Florida and measured 16 feet in length. But that is the exception. Generally they are brittle and found in small pieces that have been moved around by the wind, shifting sands and erosion.

How common are they? Good question, and one to which I do not have a definitive answer. I have no confirmation of anyone finding petrified lightning on a Vineyard beach, although the one I saw was found somewhere in Provincetown. The owner would not divulge the exact location of the find, as I think that he wanted to keep his collection spot a secret (just like you wouldn't tell the location of your buried treasure).

We do know that there are 100 lightning discharges somewhere on the earth every second, only one-third of which actually hits the ground. Considering that most of the world is not desert or beach, the chance of petrified lightning being formed decreases greatly. Add in the fact that fulgurites are coated in sand and blend into their surroundings, and the result is that finding one is equivalent to finding the proverbial needle in the haystack.

It also could be compared to finding love (with or without the fancy rock), since both are born in a flash and capture an intense instant in time.

To me these rare and elusive fulgurites might just count as a girl's best find.

Suzan Bellincampi is director of training and program development for The Trustees of Reservations.

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