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Reading about turbidity, I came across this web page with the frightening image shown below.

Text immediately before reads:

Reasons for Natural Variation

Algal turbidity varies seasonally and with depth in a complex manner as discussed previously in response to physical, chemical and biological changes in the lake. Inorganic and detrital particles from the watershed vary largely in response to hydrological events such as storms and snowmelt.

The figure caption reads:

Even relatively small amounts of wave action can erode exposed lakeshore sediments, in this case a mine pit lake from northeastern Minnesota. Can you guess what mineral was mined here?

Any ideas? I know there are bright red oxides of heavy metals like lead and mercury, certainly hope that's not the right answer.

enter image description here

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2 Answers 2

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From the red stain in the water & the rocks in the lower left of the picture it looks like iron ore.

Also, the red stain in the water appears to be a colloidal suspension, consistent with minor erosion of a bank rather than an aqueous stain caused by water reacting with sulfide minerals in the bank.

The Iron Range occurs in north eastern Minnesota.

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  • $\begingroup$ That seems to be consistent with the point of the original website. Does water ever become red from dissolved iron, or is it usually a suspension of particles? $\endgroup$
    – uhoh
    Mar 30, 2017 at 14:12
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    $\begingroup$ @uhoh: Sorry, I just noticed the additional question in the comment. Minerals/Metals do stain water, copper most definitely. Iron stains water as well. The picture in this website shows a hand basin with orange colored water that has been stained by iron. You'll see the nature of the stain is different from the one in picture in your question. $\endgroup$
    – Fred
    Feb 9, 2019 at 13:32
  • $\begingroup$ Thanks for the follow-up. Yes, that looks familliar, I think I've seen that before. $\endgroup$
    – uhoh
    Feb 9, 2019 at 13:41
  • $\begingroup$ search for instances of "iron" in bbc.com/news/world-us-canada-47165522, perhaps something to add to your answer? $\endgroup$
    – uhoh
    Feb 14, 2019 at 2:45
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Iron oxide gives the water its color. The Mesobi Iron range is located in Minnesota. It is very large iron deposit that is still mined today.

enter image description here

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  • $\begingroup$ OK! It's good to see that it's not (at least mostly) oxides of heavy metals! I wonder if the color of the photograph is a bit distorted, and should have been slightly more orange than it seems. $\endgroup$
    – uhoh
    Mar 30, 2017 at 14:09

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