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

The objective of a mineral exploration company is to discover a new and economically-feasible mineral deposit. One example is to start at a known deposit, which is too small to be economically feasible, and discover more resources that add to the deposit size. There are no nonferrous metallic mineral mines in Minnesota, but there are development projects. Listed below are general phases necessary to develop a nonferrous metallic mineral mine after exploration has discovered some 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. 
  • Evaluation 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) 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 Assessment Worksheets and/or 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 MN DNR's Mineland Reclamation webpage for more information.
  • Permitting: After Environmental Assessment Worksheets (EAW) and/or Environmental Impact Statements (EIS or SEIS) have been 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 MN DNR's Mineland Reclamation webpage for more information on this subject. 

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

Learn more:

*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.

Known Nonferrous Metallic Mineral Deposits

There are at least seven nonferrous metallic mineral deposits that are known to have:

  • significant economic interest in terms of substantial private capital investment
  • have had the delineation completed to point that a significant deposit is identified
  • have had economic feasibility or pre-feasibility studies started or completed.

PolyMet Mining: Locations of NorthMet Deposit & Potential Plant Site

Depth to Bedrock