[meteorite-list] a question on fusion crust

From: Michael Farmer <meteoriteguy_at_meteoritecentral.com>
Date: Thu, 22 Mar 2007 10:04:13 -0700 (PDT)
Message-ID: <837616.88219.qm_at_web33114.mail.mud.yahoo.com>

Crus is crust, soft, hard, it doesnt matter. It is a
crust of material caused to be on the surface of the
object by fusion.
Why would iron fusion crut not be different than that
of stones? Of course it is chemically different. You
know, you can remove the fusion crust on some stones
easily as well, so what if most of the crust on irons
is softer, and can fake off easily. The subsurface is
smooth, and much more difficult for the crust to
adhere to.
Go to Vienna and check out Cabin Creek, 100%
blue-black fusion crust on the most beautiful iron
fall I have ever seen. It is not rust, nothing but a
crust caused by intense burning in the atmosphere.
You can debate over the chemical composition of the
heat altered layer on the surface of irons all you
want, but it is fusion crust.

Michael Farmer


--- Armando Afonso <armandoafonso at oniduo.pt> wrote:

> In that case, you get a vitrification of the
> silicates, with some inclusion
> of reduced iron, eventually coming from the
> pyroxenes or olivine, giving it
> the dark tone.
> Anyway, we are really speaking of diferent and new
> minerals.
> Normally that crust is harder than the meteorite in
> itself.
> AA
>
> ----- Original Message -----
> From: "Michael Farmer" <meteoriteguy at yahoo.com>
> To: "Armando Afonso" <armandoafonso at oniduo.pt>;
> <meteorite-list at meteoritecentral.com>
> Sent: Thursday, March 22, 2007 4:48 PM
> Subject: Re: [meteorite-list] a question on fusion
> crust
>
>
> > But made from the matrix component. burned
> material
> > from the parent body, regardless of how it is
> > chemically changed, same as the fusion crust on
> any
> > meteorite. Take a Eucrite like Stannern for
> example,
> > white interior, yet the fusion crust is glossy
> black.
> > That is not soot, it is chemically altered matrix.
> > Nothing more.
> > Michael Farmer
> > --- Armando Afonso <armandoafonso at oniduo.pt>
> wrote:
> >
> >> Obviously, it is a diferent material...
> >> The external fusion crust of iron meteorites is
> >> Magnetite, the result of the
> >> combination with the air`s oxygene.
> >> AA
> >>
> >>
> >> ----- Original Message -----
> >> From: "Michael Farmer" <meteoriteguy at yahoo.com>
> >> To: "Mr EMan" <mstreman53 at yahoo.com>; "Michael
> >> Murray"
> >> <mmurray at montrose.net>;
> >> <Meteorite-list at meteoritecentral.com>
> >> Sent: Thursday, March 22, 2007 4:14 PM
> >> Subject: Re: [meteorite-list] a question on
> fusion
> >> crust
> >>
> >>
> >> > This is simple.
> >> >
> >> > Fusion, the result of material burning at
> extreme
> >> > temeratures, and crust, the layer on the
> surface
> >> that
> >> > was not there before re-entry.
> >> > Thus, FUSION CRUST
> >> > It is quite obvious that the surface of a
> freshly
> >> > fallen iron, with the blue-black coating is a
> >> FUSION
> >> > CRUST.
> >> > It generally can't be "wiped" off. I have
> pieces
> >> in my
> >> > collection, Bugoslava for example, with a .5 mm
> >> layer
> >> > of blue-black fusion crust, that survived
> cutting
> >> and
> >> > polishing of the meteorite, so it is not exacly
> >> > "soot". Of course the crust is the same as the
> >> parent
> >> > material, even on stones. How could it be of a
> >> > different material? How could an object,
> falling
> >> > through the atmosphere, get coated with
> anything
> >> but
> >> > it's own matrix as it burns? Yes, the silicates
> >> can be
> >> > altered due to heating, while irons tend not to
> >> > chemically alter.
> >> > Elton, I think you are about the only one in
> the
> >> world
> >> > that thinks fresh fallen iron meteorites do not
> >> have
> >> > fusion crust.
> >> > Michael Farmer
> >> >
> >> > --- Mr EMan <mstreman53 at yahoo.com> wrote:
> >> >
> >> >> The "soot" coating you are talking about is
> >> mostly
> >> >> freshly created magnetite (micro /nano
> crystals)
> >> >> from
> >> >> the oxidation of iron whilst passing through
> the
> >> >> incandescent phase. It adheres by magnetism
> and
> >> can
> >> >> be wiped off with rough handling. There is
> >> probably
> >> >> a
> >> >> carbon component however graphite turns to
> carbon
> >> >> dioxide upon burning >
> >> >> There are several other terms for the zone
> >> >> associated
> >> >> with "ablation" heating, one of which is in
> the
> >> >> literature: "zone of thermal alteration". When
> >> there
> >> >> is an oxidation coat
> >> > .
> >> > native elements such as
> >> >> found
> >> >> on sodium or phosphorus it is sometimes called
> a
> >> >> rind.
> >> >> This is what I favor to describe the coatings
> on
> >> >> irons--the one before terrestrial oxidation
> also
> >> >> known
> >> >> as rust.
> >> >>
> >> >> In my view there can be no crust when the
> >> chemical
> >> >> and
> >> >> physical characteristics of the surface do not
> >> >> differ
> >> >> from the donor material. That lets the door
> open
> >> >> for
> >> >> irons having crust and at least most agree
> that
> >> it
> >> >> is
> >> >> unlike the fusion crust of stoney meteorites.
> >> >>
> >> >> While at the Smithsonian inspecting the
> >> collection
> >> >> up
> >> >> close and personally, I was advised to use
> >> caution
> >> >> in
> >> >> examining a fresh iron as the coating would
> rub
> >> off
> >> >> easily. They didn't call it fusion crust but
> the
> >> >> issue
> >> >> never came up. The point being, not everyone
> is
> >> in
> >> >> agreement nor is there universal usage.
> >> >>
> >> >> Critical analysis on the assumptions about
> fusion
> >> >> crust on irons would likely lead to a more
> >> >> descriptive
> >> >> table of composition and relate that to the
> >> >> metallurgy
> >> >> and chemical composition of the meteorite
> itself.
> >> In
> >> >> fact I believe research on crustal petrology
> >> would
> >> >> be
> >> >> reveling for all types of meteorites. I yet
> >> wonder
> >> >> why
> >> >> some lunarites have a brown bubbly crust. The
> >> crust
> >> >> of
> >> >> a iron meteorite on Mars will be different
> from
> >> one
> >> >> here and I'd like to know what to expect and
> why.
> >> >>
> >> >> Intuitively, I know there would be rare
> minerals
> >> >> such
> >> >> as nickel oxides,nitrates, phosphates perhaps
> >> even
> >> >> a
> >> >> sulphide and yes even O3 and O4 silicates.
> >> However
> >> >> current wisdom is that crust is crust ego no
> >> >> research
> >> >> needs to be contemplated-NOT.
>
=== message truncated ===
Received on Thu 22 Mar 2007 01:04:13 PM PDT