Photogenic blasting grit

Some people go through the ritual of making new year’s resolutions. I don’t. Instead I try to seize on the urge to reform when the urge is fresh, and that can happen at random times during the year. On January 1, my urges are more predictable: please, no more cookies.

That’s not to say I don’t have a new year’s ritual. I do. I take down the old wall calendars and put up the new ones.

In recent years, I’ve been fortunate enough to receive a calendar from a geologist friend, Kate Clover. Kate and several others, including photographer Leo Kenney, create a calendar with photos of sand from around the world. I’m pleased to say that sand I collected inspired a photo in their 2012 calendar. The sand, dredged by the U.S. Army Corps of Engineers, came from the Mississippi River near the I-35W bridge.

Sand dredged from the Mississippi River at the I-35W bridge. Photo by Leo Kenney

Last spring, Kate and Leo offered preliminary ideas on what was in the sand, but they revised their thinking on the identity of the black, hollowed-out orb in the lower right of the photo. Originally they thought it might be buckshot, but now they think it’s sand-blasting grit.

On a sunny, unseasonably warm January day, I spent an hour browsing through abrasive blasting websites, and I think it’s likely that the sand-blasting grit in my Mississippi River sand was manufactured in China. One website described abrasive blasting this way: it “uses mechanical energy to hurl particles at high speeds against metallic and non-metallic surfaces, removing paints and other organic coatings.”

Somebody at some time in the fairly recent past repainted or removed rust from a Minneapolis bridge, probably the old 35W bridge, or perhaps a bridge upstream. At least some of the blasting grit wound up in the river.

It was clear last spring that the sand grains in this sample showed great range in their geologic provenance, less so in geographic origin — they all came from points north. But if I’m right that the grit came from China, the sand grains in our Midwestern river are much more the world travelers than I thought.

See Leo Kenney’s sand photo gallery for a peek at just how beautiful and variable sand can be.



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