[meteorite-list] Park Forest Chondrules

From: mafer <mafer_at_meteoritecentral.com>
Date: Thu Apr 22 10:25:45 2004
Message-ID: <006701c32464$c2ac30e0$6501a8c0_at_vs.shawcable.net>

Hi Greg, Steve and List

Most use a petrological microscope. These have built into them a polarizer
and analyzer, a Bertrand lens, a condenser with flip concentrator and
adjustable diaphragm, and a graduated, rotating stage for measuring angles
and a slot for various plates (such as 1/4 wave , quartz wedges ect). These
are the main differing parts for optical analysis from a regular microscope.
There are many brands available, but I understand that some aren't as
desirable as others because of how or what they are built with.

If all your interested in is seeing the crystal structure, you can actually
use any compound microscope (maybe like the one you have) and just add the
polarizer and analyzer which are linear polarizing filters, one goes above
the specimen, the other below and they are oriented at 90 degrees to each
other to provide maximum extinction (darkening).
 I picked up a used and incomplete Vickers off Ebay and restored it to
usefulness by adding the missing parts (not original by any means, the stage
is a zeiss and the lower polarizer is actually a camera polarizer which fit
my lens holder and the abbe condenser I'm not sure of the make off hand). I
think theres only one lens which is a Vickers, the rest are by various
manufacturers and this makes for a minor problem as each has to be focused
individually. But it works and does what its suppose to do and I was able to
do this for under $250, which I felt was a fair price since used through
dealers once can expect to pay a $1000 or more for a simple petrological
scope and on ebay they usually go for over 400. And new, they start around
5-10k and go up quickly from there.

Hope that helps
Mark



----- Original Message -----
To: Greg Redfern <gredfern_at_earthlink.net>
Cc: Meteorite-List <meteorite-list_at_meteoritecentral.com>
Sent: Tuesday, May 27, 2003 12:58 AM
Subject: RE: [meteorite-list] Park Forest Chondrules


> Greg,
>
> I purchased a new off brand microscope on e-Bay a few years agp for
> around $260 and using used photographic filters, built my own cross
> linear polarizer. It works well, however the MBC-10 that Michael
> Blood offers on his website as well as Jim Tobin's polarizer are
> definitely on my wish list.
>
> Steve
>
>
> --- Greg Redfern <gredfern_at_earthlink.net> wrote:
> > Steve, Bernd. List,
> >
> > What microscope do you use to view meteoritic specimens? I am
> > looking for
> > recommendations for purchase.
> >
> > Thanks.
> >
> > All the best,
> > Greg Redfern
> > 2003 NASA Solar System Ambassador
> > http://www.jpl.nasa.gov/ambassador/
> > IMCA #5781
> > www.meteoritecollectors.org
> > Meteoritical Society
> > www.meteoriticalsociety.org
> >
> >
> >
> > -----Original Message-----
> > From: meteorite-list-admin_at_meteoritecentral.com
> > [mailto:meteorite-list-admin_at_meteoritecentral.com]On Behalf Of
> > Steve
> > Witt
> > Sent: Sunday, May 25, 2003 6:07 PM
> > To: bernd.pauli_at_paulinet.de
> > Cc: Meteorite-List
> > Subject: Re: [meteorite-list] Park Forest Chondrules
> >
> >
> > Bernd,
> >
> > I just spent a while at the microscope, (first time since March 26,
> > shame on me), and I'm seeing exactly what you're talking about. The
> > vast majority, (app 90%+) in my slices anyway, have the same
> > orientation. Another thing I'm seeing that's really neat is that
> > the
> > bars in the barred olivine chondrules seem not to be running in a
> > straight line as I'm used to seeing, but rather have a swirl, again
> > following the shock orientation! Gotta get more time at the 'scope.
> > Hope to post a link to some images later.
> >
> > thanx,
> > Steve
> >
> >
> > --- bernd.pauli_at_paulinet.de wrote:
> > > Hello Listees,
> > >
> > > Although the entry in Met.Bull. 87, 2003 says that there are no
> > > visible chondrules in hand sample, one of my specimens from
> > > Steve Witt does have a few easily discernible chondrules. Now,
> > > assuming they are really chondrules, the astonishing thing about
> > > them is that they are all slightly oval and seem to show a
> > > preferred
> > > orientation (as if they were "going with the flow" of the dark
> > > parts
> > > of the matrix material). Any comments?
> > >
> > > Best wishes,
> > >
> > > Bernd
> > >
> > >
> > > ______________________________________________
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> > > Meteorite-list_at_meteoritecentral.com
> > > http://www.pairlist.net/mailman/listinfo/meteorite-list
> >
> >
> >
> > =====
> > Steve Witt
> > IMCA #9020
> >
> > http://www.meteoritecollectors.org
> >
> > __________________________________
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> >
>
>
>
> =====
> Steve Witt
> IMCA #9020
>
> http://www.meteoritecollectors.org
>
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Received on Tue 27 May 2003 11:28:55 AM PDT