Did I say that fulgurites were formed by te Tunguska event? Nope. Don't recall that. I would really only expect fulgurite formation AS I'VE SAID PREVIOUSLY in loosely compacted sandy area. Fulgurites are a glassy root-like material formed by the current running through sand. I somehow doubt that fulgurites would be formed in loamy forested (read: non-sandy) areas. I would assume that fulgurites would best be fored in desert areas, or on beaches where there is plenty of sand capable of forming the glassy strutcures that compose fulgurites.

Most of the sources I skimmed on Tunguska said the spherules were hematite, and possibly some other at least partly metallic compositions. But I'd be interested to know of what else was found. :)

And I'm not saying lightning is the ONLY thing that can form spherules, but it has been pretty well shown that electricity does cause spherical objects to form, or previously non-spherical but magnetic/conductive objects to compress into a more or less spherical shape. So, at the least it's ONE possible cause of spherule formation where there is known electrical activity. There may be other causes, as you say. I'd be interested to see resources on spherule formation by other processes. IE, what we know about HOW they form in general. Is it strictly by compression, or is it compression into plasma followed by...? What? Why do they end up spherical? Does copression ito plasma make the plasma material magnetically reactive nd electrically conductive? If so, perhaps it's a synthesis of both modalities. IE, the impactor generates plasma, which is conductive, and from there electromagnetism takes over to compress things and cause them to become spherical? Just a thought. :)