Cliff Violets
Yesterday (May 9, 2020), Sandy and I went up to Lake Manganese, which is just outside of Copper Harbor (and about 50 miles north-northeast of our house). We were mainly going up there to find the remains of the former manganese mine[1]. The last stretch was a two-track trail that I didn’t want to drive my car over, so we walked in. Once we got close to our destination, there was a series of cliffs bordering the trail, mostly going through an outcropping of Copper Harbor Conglomerate[2]. Here is one stretch of the cliff, with Sandy at the base of it for scale:
We stopped here because Sandy had spotted something interesting growing in the cliff. In this next picture, do you see the horizontal crevice near the top of the picture, with traces of greenery growing in it?
I tried to get a closer shot of the plants growing in there by basically waving my phone over my head and snapping pictures blind, which did show that there were some flowers, but weren’t good enough to really see what kind of flowers.
So finally, I had to boost Sandy up there so she could get pictures with her phone, and now we could finally see what they were – violets!
Specifically, they look like Great-Spurred Violets, Viola selkirkii.
Minnesota Wildflowers has a map showing that these are native to the Keweenaw, and ‘not rare’, so I’d say this is a likely ID. These are clearly some of our earliest-blooming wildflowers, seeing as how there were still some snowbanks in the woods when we were up there, and the trees are still a long way from being leafed out. These violets are clearly tenaceous little rascals, growing in a cliff face like that where pretty much the only other things growing are lichens.
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[1] This was, in a sense, a business expedition. I have been working on a bacterial leaching process for extracting iron and manganese from low-grade ore bodies, and I wanted to see whether I would be able to get samples of manganese ore from up there to use in my experiments. The answer appears to be “yes”, we found a lot of nice chunks of matte bluish-black rocks that feel denser than other minerals and are moderately electrically conductive, which I am nearly certain are one of the manganese dioxide minerals (probably pyrolusite). This was never actually a full working mine, it was prospected back around 1881 and 1883, removing a few hundred tons of ore for assaying and testing before deciding it wasn’t attractive enough to mine. If the process I am working on pans out, I hope to be able to recover metal from low-grade deposits like this with a minimum of capital investment, surface disturbance, or environmental impact. In fact, it would be not so much like conventional mining, and more like a farming operation, gradually leaching manganese out of the rock over a period of time and harvesting the precipitated metal oxides at intervals.
[2] The Copper Harbor Conglomerates are a band of sediments consisting of what look like smoothed beach rocks ranging from fine gravel to fist-size rocks, cemented together by what looks like lava flows. These rocks run all the way from Isle Royale down through the Keweenaw Peninsula, with many outcroppings along the way. There are outcrops just down the road from our house, in fact. The conglomerates around Lake Manganese look different from elsewhere, as they are colored blue-black, probably by manganese oxides. Elsewhere, they tend to be more red. A lot of the copper deposits in the area are hosted in the conglomerates, and so they have attracted a lot of geological interest. The rocks look interesting, but outcroppings weather away pretty fast as the pebbles pop out of the cement that they are embedded in. From the fact that the Keweenaw Peninsula is currently one of the most geologically quiet places on earth, the fact that the conglomerates are associated with lava flows tells us that they are really, really, really, really old.
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Lovely
What’s the timescale, for such a “farming” technique? I’d imagine tens of years just to allow the oxidation to take place? Does it require pumping any liquid through the rock to bring out the metal oxides?
The timescale is what I need to find out. After all, if I already knew exactly what was going to happen, it wouldn’t be research, would it?
I am anticipating that it would take anywhere from a couple of weeks to a few months to get the process going satisfactorily, and leaching to continue for some years. And yes, I’d basically need to inject swamp water into the rock to provide nutrition for the bacteria doing the dissolution.