I've read that cloud-to-ground lightning can create fulgurites. Does ground-to-cloud lightning also create crystals within the earth as it surges through the minerals?

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    $\begingroup$ Are you asking if crystals are created because lightning strikes them? $\endgroup$
    – Gimelist
    Feb 22, 2017 at 3:09
  • $\begingroup$ Melissa, I tried to clear up what you were asking. Please check to make sure it's still asking what you were interested about. $\endgroup$ Feb 22, 2017 at 10:54
  • $\begingroup$ I took out mention of negative and positive lightning... I'm strongly certain they have nothing to do with which direction the lightning moves; you can get positive CGs or negative CGs, and probably positive and negative GCs as well. This discussion reflects this. I looked to find better diagrams/videos, but unfortunately there isn't great stuff coming up. The mistaken connection between positive/negative strikes and CG/GSs are a common misunderstanding it seems. If you do wish to learn more about this topic, perhaps ask a separate question. $\endgroup$ Feb 22, 2017 at 11:07
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    $\begingroup$ Fulgurites are most definitely not crystals, but instead Lechatelierite, in simple terms glass, or bits of soil cemented by glass. $\endgroup$
    – Spencer
    Feb 26, 2017 at 2:56
  • $\begingroup$ Though perhaps not entirely crystalline, fulgurites may contain very rare elemental metals likelier to be found in outer space, like native silicon. The extremely reducive environment of a lighting strike does amazing things to (the right) rocks! $\endgroup$ Apr 27, 2017 at 3:59

1 Answer 1


I would assume that any lightning bolt connecting to the ground would be capable of producing a fulgerite in the soil, regardless of the direction that the bolt "flows". Fulgerites are caused by the extreme heat of the lightning bolt, which fuses the soil (sand mainly) together into a type of glass. Since the extreme heat of a lightning bolt also causes the sound of thunder, it's safe to assume if you hear thunder from a ground to cloud strike, it can also cause a fulgerite.

Most ground to cloud lightning seems to flow from the highest points of very tall objects, such as sky-scrapers, radio towers, etc. Since the best fulgerites are formed in sand, it may be very hard to find a fulgerite caused by ground to cloud lightning. Perhaps on a sandy mountain peak?


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