Now there's a $27.87 dollar word if I ever heard
one-------------autodidactly
One who is self taught. WOW
----- Original Message -----
From: "MEM" <[email protected]>
To: <[email protected]>; <[email protected]>;
"Greg Stanley" <[email protected]>
Sent: Monday, November 23, 2009 12:12 AM
Subject: Re: [meteorite-list] Ablation Zone 5 Layers...AND Crust
- Greg Stanley wrote:
See Fig. 1 on this UCLA web page.
http://www.ess.ucla.edu/research/cosmochem/meteorite.asp
Not sure if Dr. Wasson has written any papers regarding
fusion crusts on irons, but I would think he would endorse
anything on the web page.
So Gregg, if your statement is true, Dr.Wasson and/or UCLA endorses the
formation of "rusty" fusion crust actually formed during decent? ( Fig 1
or is it the regmaglyts that formed during passage and they are on top of
the rusty fusion crust?)
The issue is deeper than the semantic arguments, glossary obsolesence and
lies in the differences of origin, composition, and presence of crust on
different classes of meteorites. In the old school, a crust is generally
removable from the underlying substrate and a dipping in molten metal
alloy pushes the envelope of being a crust, however Buchwald illustrated
that this was a combination of free metal and oxides. I conceed that
irons--most all freshly fallen ones anyway , do have a fused surface that
we can by convention call "crust" but the question remains as to what is
the crust which is a few microns thick versus coatings and halos etc.
There is danger of promoting ignorance by making assumptions that
everything which is called crust is identical.
I am old school and I have the (un)reasonable expectation that where a
distinction does lie, that the collector can understand why things are the
way they are and not abuse the descriptions when they try to peddle their
specimens. Very few understood the distinction of silicate content when
addressing irons as the presence of silicates,oxides, carbides,phosphides,
etc largely govern the nature of a particular crust and gives insight into
what went on during that miliseconds of exposure when the final surface
was formed.
Why it matters to me is 1) the abuse of the term in describing meteorite
conditions 2) the science of understanding the differences in crust origin
and composition and 3) how do we make the distinction amongst flight
markings and do they differ from "fusion" crust?
I am satisfied that 1)one of the iron specimens cited in this discussion
apparently do have a silicate content that provided for a glassy fusion
crust and its origin is intriguing scientifically. 2)That by definition
alone (fused + coating) the irons do routinely have a "fused
coating/crust" which differs significantly from our traditional concept of
"crust" even though it is indistinguishable from the interior to the naked
eye. (Do folks really "see" the crust or do they see if because it is
supposed to be there?) At what point in weathering do we "see" that the
welded crust/layer on an iron has rusted away given it is a few microns
thick? 90% of the time, the seller will be claiming "crusted" long after
the crust is gone, IMO.
I've seen little to nothing so far that invalidates describing the
ablation zone nor crust in layers--Nor did Buchwald, apparently.
Finally, the term "big-head" someone used probably translates to
"arrogant" Either way it was used in error as I was misunderstood. I did
not disparage the pioneers in the field or meteoritical study. They
gained their meteoritical knowledge largely autodidactly when they came
over. I mentioned their former fields because when an individual crosses
over into a different field of research, one can not just presume that
they immediately acquire the entire knowledge base of those who were
formerly educated in the same field.
Elton
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