From Exploration to Development:
The Development Process for Nonferrous Metallic Minerals

Drill Core Library

Public meeting in Blaine, MN regarding the Environmental Impact Statement (EIS) for PolyMet's NorthMet Project (12.10.2009)

There are no nonferrous metallic mineral mines in Minnesota, but there are development projects. A mineral development project must move through several steps before mining is allowed. The government regulates the environmental review and permitting steps, as well as some business activities. However, the developer must also prove to its investors that there is a profitable mine scenario, which requires significant engineering, design, planning and economic analysis. Listed below are general phases necessary to develop a nonferrous metallic mineral mine after exploration has discovered mineralization:

Discovering a mineral prospect
Finding mineralization in a few drill cores, no matter the richness, does not make a mineral deposit. At this point, the site of mineralization would be called a mineral prospect.

Investigative drilling
After initial favorable results, a time-consuming (multi-year) and expensive (millions of dollars) program of follow-up core drilling and assaying must be conducted to prove out the areal extent, thickness, depth below surface, and concentration of metals (grade or weight %) before it can qualify as a mineral deposit.

Preliminary economic assessment
Whether this mineral deposit can be economically mined will require that the value of the defined ore body be compared to the labor and capital costs related to building the mine and processing facilities, mining and transporting the ore, crushing and processing the ore, recovering the metals, developing sound environmental mitigation, financial assurance for the permit, and planning for mine closure.

  • Environmental baseline testing 
    To properly evaluate the costs listed above, environmental baseline testing must be conducted and a mitigation plan developed.
  • Metallurgical testing 
    Metallurgical testing must be done to determine whether the metals can be separated from the particular type of rock, and at what cost.

Economic feasibility study
A complete economic feasibility study will incorporate all steps needed for the overall plan from the start of mining to the point of product sales to mine closure.

Capital investment
Raising capital for building the mine and facilities, which is usually in the range of hundreds of millions to billions of dollars.

Environmental review
Environmental Impact Statements are required for new mining proposals and are often required for expansions or substantial changes to existing operations as stated in Minnesota Rules, part 4410.4300, subparts 11-12 & Minnesota Rules, part 4410.4400, subparts 8-9. These rules were adopted under the Minnesota Environmental Policy Act, MN Statute 116D. See DNR's Mineland Reclamation webpage for more information.
DNR's Mineland Reclamation »

If the Environmental Impact Statement (EIS) is deemed adequate the company can submit applications for a permit to mine. Permit requirements for nonferrous mines are described in the Mineland Reclamation Rules Chapters 6130, 6131, and 6132 respectively. Again, please see DNR's Mineland Reclamation webpage for more information on this subject.
DNR's Mineland Reclamation »

There is a long list of possible reasons, such as a sustained metal price decline, as to why a mineral deposit discovery may not be developed into a mine.

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*The PDF includes embedded 'speaker notes' with additional information for select slides. The speaker notes can be viewed in Adobe Reader or Acrobat, and within the following internet browsers; Internet Explorer, Mozilla Firefox, & Safari. Google Chrome does not display the speaker notes.


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