[meteorite-list] Plessite and Schreibersite. was Widmanstatten Pattern

From: Mr EMan <mstreman53_at_meteoritecentral.com>
Date: Tue, 8 Sep 2009 18:54:29 -0700 (PDT)
Message-ID: <716973.53775.qm_at_web55205.mail.re4.yahoo.com>

As the ravages of time rake through my memory...some is coming back to me. The mineral Plessite is an intermediate mixture of both taenite and kamacite. It may be the bulk mineral in iron meteorites. I need to find it it is also the composition of the iron flecks in common chondrites of does that nickel-iron come in various flavors?

I am remiss for not speaking of plessite more frequently when talking about kamacite and taenite.

Its name even means filling ( Gr:plythos) It's German name is Fulleisen

Buchwald and Massalski named some varieties(according to Wikipedia):
    * acicular plessite/Type I plessite
    * black plessite/Type II plessite
    * cellular plessite/Type III plessite
    * comb plessite
    * net plessite
    * pearlitic plessite
    * spheroidized plessite

My recollections are that schreibersite favors almost exclusively taenite boundaries( I may be mistaken again) and this is where I got insight into my private hypothesis that phosphorus is a critical factor in differentiating taenite from kamacite on the macro level. I suspect(dangerous I know) that the schreibersite bands/fronts, once developed provide a catalyst zone preferential for taenite and/or nickel, drawing it through the laminae and stacking it behind the front. As the taenite builds up the front advances into the plessite so long as the temperature remains within the phase envelope. Now if I can find that envelope... I can't begin to theorize how schreibersite accreted to the band that it does when it does but it seems to have a propensity to do so. In ataxites schreibersite can form crystals plates instead of bands. Owing to its yellow brassy color my be mistaken for troilite.

I am throwing this out in case anyone has some journal articles on the subject or cares to discuss the chemistry. If and when I find the specific of past research I'll pass that along. For now I want to get the Goldman pdf file and see what I should already know at my age.

Elton
Received on Tue 08 Sep 2009 09:54:29 PM PDT