Low Magnification

Chuck,

When you’re shopping for a new ‘scope or looking to upgrade the one you have I suggest you try to include glass that will let you take low magnification pictures too. When I’m looking at slices or thin sections I move them around to get an impression of the overall piece. You can’t share that impression with folks with a single picture at medium magnification so a larger field of view is a real help. The “regular” magnification I shoot at gets me a field about 3mm wide. That works OK for fine grained achondrites or chondrites with small features like CO3s. But with an L chondrite or a CV3 you can easily have a single chondrule hogging the field. The trouble is that low magnification lenses cost a lot.

I had a workaround that I thought of as my own little secret ‘til I was found out by Larry Chitwood. Larry, a geologist and clever guy, co-authored “Field Guide to Meteors and Meteorites” with Richard Norton. I had emailed him a few pictures and he called asking about one in particular. He had opened the picture with photo editing software and for some reason had radically jazzed up some settings. I don’t know what they were – contrast, color saturation or maybe others. He spied signs of a three by three pattern and asked what’s up with that? “Did you put a bunch of pictures together to make this one?” Bingo. I’d been found out. A poor man’s low power lens is paste. Electronic paste of course.

And with it you can make pictures of chondrules as they sit assembled instead of as individuals or an overview of a Martian slide. Examples? Of course.

John

You can see how the brightly colored olivines sit in the lighter finer grained pigeonite in this Martian shergottite. There’s a reason they call them megacrysts. Some of the dark patches are olivine that is in optical extinction and some are melt pockets.

This overall view of a diogenite sample shows large grains and a continuum of smaller and smaller fragments.

It would be hard for a close-up of this howardite to show the range of grain sizes along with those dark areas.

Howardites are from the plowed surface of Vesta so you expect to see a variety of things. This sample has a small patch of needlelike crystals on a dark background midway along the diagonal edge. There’s the dark clast, of course, and a couple lighter ones more toward the right.

D’Orbigny, an angrite, is spectacular in regular views with its bright colors and skeletal crystals. Here, at low magnification, we see that those pictures are not just isolated glamour shots. The whole thing sparkles. And check out the vesicle!

Olivine grains in the Huckitta pallasite are pretty large so I had to fit several pictures together to get this stained glass view.

Ah! Back to chondrites. Korra Korrabes is brecciated but you have to get a wide enough view to see the light clast, the H3 groundmass and a couple chondrules for scale.

Same story here. This Chergach H5 thin section has “rivers of melt”. It helps the story to show both river banks plus chondrules on the shore for scale.

Chondrule low magnification library. Saratov L4

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About the Author

John Kashuba
John is a natural history enthusiast living in Oregon.
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