Ores, mining, and the legacy

Environmental Geology lecture outline

Content:

Figure of the Hibbing Iron Mine in Minnesota. You are viewing about one third of the mine which is some 6 miles long. The red coloration is due to oxidation of the iron ore. Open pit mines such as this one often excavate beneath the water table. Like a hole deep enough in beach sand they can often fill up with water, and can lower the groundwater table in the area when they are active. Dewatering is an important part of mine operations.


Introduction

Where and why of ore deposits = discipline of Economic Geology.

Importance of metals and ores to society:

This is a figure showing some of the tailings (waste rock) associated with Hibbing iron mine in Minnesota. The blue arrows point to the long ridge that is composed totally of waste material from the Hibbing mine. The student stands on more tailings. Much of it is sand/gravel overburden, and relatively benign, but this gives you an idea of the volume of earth material involved. For many metallic deposits the percent of rock that is the ore mineral is a few percent by volume, and the remaining amount is waste rock.


Cradle to grave perspective on metallic resources

Useful framework = cradle to grave environmental perspective includes exploration, extraction, processing (often smelting), manufacturing, disposal and/or recycling.


Legacy of abandoned old mines

In Montana and Colorado are particularly well know, 1000s of sites across the country that were mined before the era of environmental awareness.

2015 Colorado - Gold King Mine waste water spill - https://en.wikipedia.org/wiki/2015_Gold_King_Mine_waste_water_spill .

Animas river in Colorado 24 hours after mine release. Image source: https://en.wikipedia.org/wiki/2015_Gold_King_Mine_waste_water_spill#/media/File:Animas_River_spill_2015-08-06.JPG .

USGS site on a related initiative - http://www.usgs.gov/themes/factsheet/095-99/ .

Mine in Montana, which prides itself on its trout streams. Image source: http://toxics.usgs.gov/photo_gallery/metals_variation_all.html


Two specific examples of ores

Aluminum as an example:

Uranium as an example:

 


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