[Rockhounds] fulgurites

[pmodreski at aol.com]

It's been interesting to read everyone's comments about fulgurites; I've just been catching up on my Rockhounds email, after being very tied up with the Denver Show, a preceding mineralogical conference in Golden, and having been away visiting my family in New Hampshire the week before that.

You bet, lechatlierite is for sure a mineraloid.? The name is "traditionally" mentioned in mineralogy books, but it definitely is not found in sources such as the Glossary of Mineral Species, which only list bona fide approved mineral species.? Lechatlierite occurs in fulgurites, and has also been recognized in some impact-deformed rocks, subject to intense pressure and temperature.? A somewhat analogous term is maskelynite, which is glassy (melted) plagioclase feldspar from shock impact, known from some meteorites and (according to Mindat.org) from at least one terrestrial impact structure.? I don't know if there is another such name, for melted potassium feldspar.

I've been interested to read people's comments about searching for, and finding, fulgurites.? I've always considered that they are quite uncommon and very hard to find, and, like meteorites, I think almost all have been found by accident, not by anyone's systematic searching.? (That statement used to be true for meteorites but no longer really as, in view of the large number that have been found in Antarctica, as well as in the Sahara.)

Something that I have puzzled over, is, what proportion of lightning strikes, actually produce fulgurites?? I'm not sure that anyone really knows this; there are thousands of lightning strikes every day, worldwide; but I'm not sure if anyone knows if it does or doesn't take special conditions of soil/sand type, moisture, etc., to make a fulgurite.? It's likely that in many instances, the lightning discharge may travel first through other material (such as trees and tree roots) down into the ground before it begins to melt sand and form a fulgurite, so many fulgurite may be "hidden" underground, and would not be found or noticed unless someone excavated in the right spot where there had been a lightning strike.

Likewise a puzzle--and we have talked about this before on this List--is how common it is for lightning strikes on rock outcrops, to produce a fulgurite.? One always reads "anecdotally" that there exist melted patches on rocks near mountain summits where lightning has struck, but I am still not sure that I have ever actually seen a picture of such a thing (much less see one in person), or read any definitive documentation that ANYWAY has ever really seen such a thing.? My suspicious is that most lightning strikes on mountains, if they do not hit trees, go to the crevices between rocks where moist soil is likely to be more conductive, and that any melted rock that forms, may be in the form of rock fragments contained in the soil down beside or in cracks within bedrock.? The closest I've seen is one specimen, in Kreigh's collection, of a small piece of granite "from the Colorado mountains" partially melted by lightning; but I don't believe the source of his specimen had provided any specific information of how/what/where this actually occurred.? A few years ago, some collectors brought a large fulgurite specimen to the Denver Museum of Nature & Science, from a lightning strike on a ridge high above Boulder Canyon, in Colorado (the Museum subsequently acquired the specimen); it was from a lightning strike I believe at a tree stump, and the fulgurite was excavated by digging out the crevices between and beneath the rocks around it; I don't think any actual melted rock was observed on exposed rock surfaces.

Pete Modreski



-----Original Message-----
From: kugeln at peoplepc.com
To: Rockhounds at drizzle.com: A mailing list for rock and gem collectors <rockhounds at lists.drizzle.com>
Sent: Mon, 15 Sep 2008 6:17 pm
Subject: Re: [Rockhounds] fulgurites


Fulgurites are one of the very few mineraloids that are a true glass. The glass is known as LeChatelierite. Pete Modreski, correct me if I'm wrong.?
?
----- Original Message ----- From: "ROBERT A SANTEE" <timeman123 at optonline.net>?
To: <rockhounds at lists.drizzle.com>?
Sent: Monday, September 15, 2008 6:19 AM?
Subject: [Rockhounds] fulgurites?
?
> Hi can anybody give me any info how I can find fulgurites I just started > to collect them and I thought it would be great to look for them.I live in > New Jersey and I do not no if that would be a good area to collect them > any info would be great thanks bob.?
>?




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