An Article In Meteorite-Times Magazine
by Tom Phillips
Mount Tazerait inclusion, A renaissance in thin sections!
Mount Tazerait L5 This meteorite fell August 21, 1991. Quite a beautiful meteorite in cross polarized light but for this article I am ignoring the typical and focusing on one unusual inclusion. It is circled in green in this photo of the thin section. Which, by the way, is an example of Jeff Hodge's obsession with perfect thin sections. I think he is resetting the standards.
I like to image the material at magnification levels higher that what is necessary for classification. It has become more about chasing the perfect image than traditional petrographic examination. I had lamented about needing a higher polish on a couple thin sections and offered to further polish one uncovered thin section of Jeff's I was working with. He rose to the challenge and so did his thin section maker (said to be the best in the world) and the next thing I know, Jeff has new standards and nomenclature to go with them.
This was an excerpt from a recent email from Jeff. I think Jeff deserves recognition for this. These changes do not come cheap and prior to these new thins by Jeff, I hade never seen or even heard of ANY made to these standards. When he states polished he is talking about 1/4 micron! DPU , which is discussed in a previous email is Double polished uncovered.
Note on Quality: Any covered slides produced from this batch on have been upgraded to DPC and no longer SPC as is the standard.
These new DPC slides exhibit much higher degrees of clarity and sharpness. You will notice the difference.
DPC- double polished covered (polished on both sides, the side attached to the slide as well as the top surface. then covered.)
SPC- single polished covered. This is the norm. (only the top side is polished. Then covered)
This thin section is a DPC. I have had the privilege to examine several others including Lunar and Martian so look for some awesome micrographs coming soon!
Also note, I am only showing inclusion micrographs in this article. Look to my Gallery where I will post many more images including some of the typical structure.
This is the inclusion at 85X viewed in cross polarized light. I seldom post images at this low of a magnification because I am really not that good at it. I had to show at least one shot at this level to give you a perspective as we get closer.
My old favorite, 160X! You will notice I favor this magnification in my previous work. But, since Jeff has upgraded the thin sections, my new favorite is now 400X and 760X!
OK. this is where it starts to get interesting. Especially when you compare to the lower magnification shots. These next 4 were taken at a magnification of 400X.
The sweet spot! These images are taken at 760X. Look at the detail and keep in mind this is 760X then go back to the 85X to compare.
Finally I finish off with 2100X. I am using an oil immersion lens and tweaking everything. While not as beautiful in a strictly "eye candy" sort of way, these shots open up a whole new set of observations. Maybe it's just me, but I think there might be information to be learned from these methods as well.
Let me know what you think! Perhaps you could post a comment to the Meteorite List to get others to look. I think Jeff has started something!!!
Special Note from Jeff Hodges-
These new high quality slides are available for purchase from Anne Black at www.impactika.com. Our goal is to provide the highest quality thin sections to collectors, universities, museums, etc. Her site is the only place anyone can purchase this new generation of thin section now that David New is no longer in business, she is now the leading source for quality.
Tom Phillips can be reached by email at:/font>
The Tom Phillips Microscopic Meteorite Photography and Gallery>