Fulgurites (from the
Latin"fulgur" meaning thunderbolt) are natural hollow carrot-shaped glasstubes formed in quartzose sandor soil by lightningstrikes. Fulgurites can also be produced when a high voltage electrical distribution network breaks and the lines fall onto a conductive surface with sand beneath. They are sometimes referred to as "petrified lightning." The glass formed is called lechatelieritewhich may also be formed by meteorite impactand volcanicexplosions. As it is amorphousit is classified as a mineraloid.
The tubes can be up to a couple of centimeters in diameter, and meters long. Their color varies depending on the composition of the sand they formed in, ranging from black or tan to green or a translucent white. The interior is normally very smooth or lined with fine bubbles; the exterior is generally coated with rough sand particles. They are
rootlike in appearance and often show branching or small holes. Fulgurites occasionally form as glazing on solid rocks (sometimes referred to as an "exogenic fulgurite" [ [http://findarticles.com/p/articles/mi_m0GDX/is_5_79/ai_n6248984/pg_1 Exogenic fulgurites from Elko County, Nevada: a new class of fulgurite associated with large soil-gravel fulgurite tubes] ("Rocks & Minerals", Sep/Oct 2004, Vol. 79, No. 5.)] ).
Fulgurites are a very rare phenomenon. A very large one was found in
South Amboy, New Jersey. This was roughly nine feet long with a diameter of three inches (7.6 cm) near the surface of the ground, and tapered to roughly three sixteenths of an inch (5 mm) in diameter at the deepest point recovered. As is often the case due to the fragile nature of fulgurites, scientists were unable to extract it in one piece and the largest recovered fragment was a mere six inches (15.2 cm) long. Fulgurites are notably found high on Mount Thielsen("the lightning rod of the Cascade Range") where they form a brownish-green glaze on rocks (especially on the final five or ten feet of the summit pinnacle) and on the shores of the Great Lakes.
The largest fulgurite known is at the
Peabody Museum of Natural Historyat Yale University, which has on display a 13-foot (4 m) long fulgurite from the shores of Lake Congamond in northern Connecticut. The fulgurite has been on display at the Museum since the 1950s, and is viewable in the new Hall of Minerals, Earth and Space as of May, 2006. A specimen of fulgurite over 3 metres long is in the Natural History Museumin London. It is preserved in sections of over 50cm. Another museum speciment is on display in Philadelphia, USA, at the Academy of Natural Sciences; it was discovered in 1940.
* [http://environment.newscientist.com/channel/earth/mg19426102.100-the-word-fulgurite.html Fulgurites in New Scientist]
* [http://amsglossary.allenpress.com/glossary/browse?s=f&p=51 Glossary of Meteorology definitions (including Fulgurite).]
* [http://ira.usf.edu/CAM/exhibitions/1998_12_McCollum/supplemental_didactics/47.Petrified.pdf Petrified Lightning by Peter E. Viemeister (pdf)]
* [http://www.mindat.org/min-7747.html Mindat with location data]
* [http://www.minsocam.org/MSA/collectors_corner/arc/njfulgurite.htm W. M. Myers and Albert B. Peck, "A Fulgurite from South Amboy, New Jersey,"] American Mineralogist, Volume 10, pages 152-155, 1925
* [http://plaza.ufl.edu/rakov/Gas.html Vladimir A. Rakov, "Lightning Makes Glass,"] 29th Annual Conference of the Glass Art Society, Tampa, Florida, 1999
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