[meteorite-list] a question on fusion crust

[Michael Farmer]

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

> 

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