An Article In Meteorite Times Magazine
by Tom Phillips and Martin Horejsi

 

Portales Valley

Check out this slice (and the polish)! This 75 gr. slice of Portales Valley belongs to
Martin Horejsi. He has the coolest stuff!

When Martin said that this month he wanted to feature an ordinary chondrite (H6) I figured "an H6?" OK but why? A H6 typically doesn't have many features to look at because the chondrule structure is dramatically altered.

When I saw it, I honestly thought he was pulling my leg! I said "This is a mesosiderite! If you like, lets put a polish on the meso". He laughed and let me figure it out. We took it to 1/4 micron and then to a cloth wheel. We wanted to show the Widmanstatten Pattern without using acid and damaging the chondrite matrix. It worked fairly well. Did I say Widmanstatten Pattern? It is the only ordinary chondrite where the iron has Widmanstatten Pattern in it. Crystal plucking made, an easy, fine polish nearly impossible. Martin and I spent 4 hours polishing this one slice!

This amazing meteorite fell in 1998 and is classified as an H6. It is providing information on how the differentiation process works. I do not intend to "Talk smart" on this one! I just want to share some micrographs. There is a host of great articles out there. The one I liked was written by Alex Ruzicka and Melinda Hutson with the Department of Geology, Portland State University.

http://www.psrd.hawaii.edu/Sept05/PortalesValley.html

This photo was taken through a low power (20X) stereo microscope. I needed to stay relatively low magnification to show the Widmanstatten Pattern. This pattern was not brought out with acid, but rather the result of the final cloth polish. There are differences in hardness of the pattern compounds, and a cloth wheel was used to "wear down" more material in some places than others, revealing the pattern.

These are some of my favorite micrographs we took of this slice. I'm not qualified to state what is being viewed so just enjoy the images!


Tom Phillips can be reached by email at:

STARSANDSCOPES@aol.com

Meteorite Photos and Images
The Tom Phillips Microscopic Meteorite Photography and Gallery