[meteorite-list] a question on fusion crust
From: Michael Farmer <meteoriteguy_at_meteoritecentral.com>
Date: Thu, 22 Mar 2007 09:48:00 -0700 (PDT) Message-ID: <87052.81468.qm_at_web33114.mail.mud.yahoo.com> 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 12:48:00 PM PDT |
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