[meteorite-list] a question on fusion crust

From: Armando Afonso <armandoafonso_at_meteoritecentral.com>
Date: Thu, 22 Mar 2007 16:57:38 -0000
Message-ID: <002a01c76ca3$32b72180$62b0fea9_at_TOSHIBA>

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.
>> >>
>> >> Some of the oft quoted god status experts who
>> write
>> >> of
>> >> fusion crust on irons monitor this list and have
>> >> remained curiously silent on the topic. I hope
>> this
>> >> topic is thought provoking for all parties.
>> >>
>> >> I suppose that the use of the term "fusion crust"
>> >> universally with respect to irons is acceptable
>> if
>> >> one
>> >> doesn't have a need for technical accuracy. One
>> >> thing
>> >> yet to be refuted here on the list is that the
>> >> "crust"
>> >> on irons is not composed of "glass".
>> >>
>> >> Elton
>> >>
>> >> --- Michael Murray <mmurray at montrose.net> wrote:
>> >>
>> >> > Hi List,
>> >> > Are you ready for a dumb question! Here
>> goes...
>> >> Is
>> >> > there a more definitive description of the
>> >> blackened outer layer on the surface of iron
>> >> meteorites than simply referring to it as "fusion
>> >> crust"? From what I can gather looking at
>> different
>> >> pictures of stonys, they seem to have a glassy
>> or
>> >> melted layer of the material of the stone. I can
>> >> see
>> >> that being a 'crust'. On at least some irons,
>> there
>> >> is a coating but it doesn't appear glassy, just
>> >> blackened. I'm guessing that that coating is
>> >> partially resulting from burning of the gases in
>> the
>> >> atmosphere? If it is a 'crust', it is not much
>> of
>> >> one. It looks
>> >> like a very thin coating of soot that is adhered
>> to
>> >> the stone, although more durable than soot.
>> This
>> >> is
>> >> probably one of those dumb questions that the
>> >> Collection of Wisdom would answer.
>> >>
>> >> The stone in this picture has the blackened
>> layer
>> >> I'm referring to:
>> >>
>> >
>>
> <http://i127.photobucket.com/albums/p124/mmurray_02/IMG_0319.jpg>
>> >> Michael Murray
>> >> ______________________________________________
>> >> Meteorite-list mailing list
>>
> === message truncated ===
>
>
Received on Thu 22 Mar 2007 12:57:38 PM PDT