[meteorite-list] NWA 5000 micrograph techniques

From: STARSANDSCOPES at aol.com <STARSANDSCOPES_at_meteoritecentral.com>
Date: Tue, 15 Apr 2008 21:00:58 EDT
Message-ID: <c7f.1270cdcb.3536a9ca_at_aol.com>

NWA 5000 micrograph techniques
 
Hi list, I am sure many of you are not interested in the techniques I used
to produce the NWA 5000 micrographs but I have had quite a few emails (and
not all from microscope users) so I thought I would address what was unique to
this material.

The solar wind Vesicles are found in the glass and the trouble with this
glass is it is nearly completely isotropic. What that means is, when you use
cross polarized light, the glass is black and these black dots (Vesicles)
against a black back ground are hidden. So in standard full Xpol, they would be
easy to miss.

Bright Field reveals little more and no color!

Additionally, when a wave plates is applied the back ground color drowns
out the photo.

A measure of just how isotropic this glass is, is nicely shown in the fifth
image of today's Rock From Space Picture of the Day. Birefringence in the
glass would be visible by a shift in color! And when you look at the photo
with this in mind, you can see there is not much color change going on in the
glass when compared to a clear pocket.

I settled on polarizers at 45 degree with the addition of a PS3 (see this
months Micro Vision) quarter wave plate at full extinction. Slight nudges of
the wave plate off of full extinction draws out some color in the birefringent
material, making the photo more pleasant with out tinting the glass.

My Meteorite Times Micro Vision article is on the PS3 quarter wave plate.
You should check it out if you are interested in this stuff.
http://www.meteorite-times.com/meteorite_frame.htm

Tom Phillips
 



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Received on Tue 15 Apr 2008 09:00:58 PM PDT