On "regmaglypts" in LDG...
Sean M. wrote:
"I called them "Pseudo" in the description, because, well, there is
still a lot of debate about them being formed from traveling through
the atmosphere"
Hello,
"Still a lot of debate"? Could you kindly elaborate where atmospheric
aerodynamic shaping for LDG ever was (maybe) or stilli is (huh??) being
seriously debated by anyone who can tell the difference between a
tektite and a chard of a beer bottle?
==>With so many tons and never an inkling of any fusion crust or other
surface shaping?
==>With a water content indicating the glass was not formed in space
like other tektites.
In answer to the prior question, regmaglypts are usually formed dues to
differences in material as the theory goes (edges of sharp breaks get
rounded, but those shapes aren't regmaglypts - and variation of true
regmaglypting rates during its removal during ablation. Meanwhile,
tektites, and for that matter LDG is essentially uniform so the
mechanism to form regmaglypts would have to be by thinking a bit more
out of the box...
Best wishes,
Doug
-----Original Message-----
From: Sean T. Murray <[EMAIL PROTECTED]>
To: [email protected]
Sent: Fri, 4 Apr 2008 9:13 pm
Subject: Re: [meteorite-list] Atmospheric ablation marks on Tektites?
Ok folks - I want plenty of comments on this mess :) One of my favorite
topics... Let's see if I can ramble through this...
Most tektites, by definition, have passed through the atmosphere at
least once. Some material (depending on the theory you believe in) just
is spit out in the form of blobs of glass, but others take the long
trip through the atmosphere to gain their unique shapes.
There are still people on both sides of the fence as to the origin of
tektites. The majority of the folks think they happen on impact here on
earth and that the material is thrown out of the atmosphere and then
re-enters to create many of the aerodynamic shapes we see in typical
tektites. The other theory is that tektites were formed from lunar
events (such as volcanic eruptions) and enter the atmosphere on earth
and gain much of their shapes on the trip through.
There is a lot of reading material out there that talk about both
theories. The main flaw in the impact theory has to do with Stokes Law
(for creating glass) and the lack of a discovered crater for the
Australasian event (the crater should be massive considering tektites
from that event covered about 20% of the planet). The lunar theory has
it's share of problems as well. You should read Hal Povenmire's book.
It's got a lot of interesting information on tektites. I also love this
website: http://www.tektites.co.uk/index.html - there is a good set of
pages that describe the formation of the shapes and features on
tektites (http://www.tektites.co.uk/22.html).
However, in the case of LDG, a point to make is that I've seen multiple
people argue that they are not actually tektites, but are instead
impact glass. Most impact glass definitions that I have seen don't
require that the material has been in and out of the atmosphere at
least once. However, it is hard to argue with the features on the LDGs.
I have a piece that has "regmaglypts" that rival any Sikote you can
find (thanks to Mike as well!
http://www.rocksfromspace.org/March_23_2008.html). I called them
"Pseudo" in the description, because, well, there is still a lot of
debate about them being formed from traveling through the atmosphere,
or just weathering out due to natural weaknesses imposed by the
cooling, impact, and subsequent chemical etching (fresh water mainly)
and/or sandblasting over the years.
I'd love to hear some other opinions. There is another source that I
have not started reading yet - Joe McCall's book on tektites. He does
have a chapter that singles out Darwin glass and LDG.
Sean.
----- Original Message ----- From: "Michael Gilmer"
<[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Friday, April 04, 2008 10:36 PM
Subject: [meteorite-list] Atmospheric ablation marks on Tektites?
Hi Group!
While reading through another Meteorite-related
message board on the WWW, I ran across a statement by
an IMCA member that puzzles me somewhat. A discussion
about Libyan Desert Glass was ongoing, and we were
sharing photos of our LDG specimens. (and I showed
off my new 9+ gram piece of dark-veined glass from
Michael Farmer - thanks Mike!)
So the guy says :
"This is one of my favorites and is fully oriented
with regmaglypts (yes, tektite impactites can have
atmospheric ablation patterns too)."
Ok, here is my confusion - I was under the impression
that tektites were formed on impact - on Earth. So,
doesn't this mean they cannot have atmospheric
ablation patterns? Assuming the tektite never passed
through the atmosphere, I don't see how this is
possible.
I have seen tektites with features that resemble
regmaglypts and orientation, but this is just chance
occurence, right?
Or do I need to be schooled here?
Thanks in advance!
MikeG
>
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