I’ve learned two things this week:
1. Plain brown sand is never as plain and brown as it looks.
2. You really can see a whole world in a grain of sand.
A few weeks ago I collected a sample of sand that had been dredged from the bottom of the Mississippi River. I wanted to see what the river was hauling downstream.
My geologist friend, Kate Clover, looked at it and found several minerals that you would expect to find in Minnesota sand: mica, feldspar, quartz, and magnetite. She found fragments of mussel shells and bits of rock such as mica schists, basalt and agates.
But she also identified epidote. This news perked me up a little. Epidote is a pale green mineral found only in metamorphic rocks. If you compare rocks to music, sedimentary rocks are like major keys, metamorphic rocks are like minor keys. They have more mystery.
I looked up epidote and discovered that it’s contained in the same northern Minnesota rocks that contain copper and nickel — minerals that attract the mining companies. Wouldn’t it be cool if we had gem-quality epidote?
My sample of sand also contains a few things that don’t really say ‘sand.’ It has bits of concrete, green and black industrial slag (a waste product of metal foundries), charcoal, road paint, and even buck shot. I was grateful Kate didn’t find anything weirder than that, given the urban location.
Leo Kenney took a close-up photo of the sand:
The buck shot is in the middle. Kate wasn’t sure what was embedded in the divot. There are two black slag pieces — the really bubbly grain and the one almost directly below it with the shiny surface and deep black/ purple cast. The shiny greenish grain in the lower left might be slag. The large orange grain is feldspar, the smaller orange-red grain is probably agate. A lot of clear and cloudy quartz grains, some more polished than others.
This image shows off the charcoal, to the right of center, and a chunk of yellow road stripe paint with some reflective glass beads still embedded.
Here’s the camera (not exactly a point-and-shoot) that Leo uses in his macrophotography lab :
This particular plain brown sand is red, green, black, purple, orange, and yellow. It came from rocks that were once part of mountains, volcanic eruptions, and ancient seafloors. Then, as if that weren’t enough, the glaciers dragged it around and rivers pushed it downhill. And of course, we have added a few things to the litter in this fluvial litter box.
A ‘whole world’ a la William Blake.
Thanks to Kate Clover and Leo Kenney, sand aficionados, for their generous help.