An Article In Meteorite-Times Magazine
by Tom Phillips

CK - A Visual Exploration

NWA 4422 CK 3.9 S1 W2. A carbonaceous chondrite. I was fortunate two have two thin sections to examine. One belongs to Jeff Hodges and the other to John Kashuba. (Thanks for the loan, I'm treating them well!) These thin sections were polished to 1/4 micron on both sides. This is a big deal. It is hard to do and few thin sections are prepared this way because it is just not necessary. Even uncovered thin sections polished for micro probe work are not this fine. I was putting a higher polish on prepared thin sections when Jeff arranged to have some made up this way. My higher than normal magnifications really need a high polish.

Generally thin sections are used for transmitted (pass through) light examination and thick samples are used for incident (reflected) light. These micrographs were taken in incident cross polarized light at a magnification of 345X. The colors, typical of transmitted cross polarized light, are a result of the light passing through the more translucent material, bouncing off the glass slide and traveling back through the sample. No behind the slide lighting is used!

I use a 150 watt Xenon lamp to get the necessary amount of light and a Glan-Thompson Polarizer. These polarizers are made of two calcite elements cemented together and are known for their high extinction ratio. A fleck of polished highly reflective iron can be made to appear pitch black.

Let me know what you think and more importantly if you can come up with a use for this technique!

I will post these as well as conventional Xpol images of this material to my Micrograph Gallery hosted by Meteorite Times.

Since I have been away for a couple months, Paul thought it would be OK to include a few more shots.  This group of micrographs were taken of the same slides but at a magnification of 160X in combined incident and transmitted cross polarized light.  Both light paths have their own independent light sources, apertures and polarizers.
This is the way a CK should be looked at!


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