Map of of Gold in Till, Cook Area, St. Louis County

Map of of Gold in Till, Cook Area, St. Louis County


Local Copy of files: Click here to download a zip with all of the files from this article (including the map)

Data released on December 19, 2013

December 19, 2013 – DNR Open-File Project 392: Regional Survey of Gold in Till, Cook Area, St. Louis County

Summary and Data: The DNR is today releasing preliminary results from the processing and analysis of thirty-four (34) glacial sediment samples collected in Northern St. Louis County, at locations where State- or County-controlled surface ownership overlies State-owned or State-administered mineral rights. This is the latest data release for a DNR geological investigation that began in July, 2012, within an approximately 200 square mile area of historical gold and base metal exploration that lies between Cook and Tower.  In this region, an Archean granite-greenstone terrane is overlain by relatively thin layers of Rainy Lobe till and other glacially-derived sediments.  These are ideal geological conditions for using gold grain counts and heavy mineral geochemistry in glacial sediment samples to explore for proximal bedrock mineralization.

The 34 glacial sediment samples were collected in October 2013, and sent to Overburden Drilling Management, Ltd, (ODM) for heavy mineral concentrate (HMC) separation and gold grain counts.  Sample locations were based on initial results from 105 glacial sediment samples that were collected within the project area in October 2012, processed by ODM, and assayed by Activation Laboratories Limited (ActLabs). The DNR released those results to the public on February 4, 2013 and July 2, 2013.

Today’s data release includes an ODM report dated December 5, 2013 that documents HMC separation and gold grain count work for the 34 new samples, a sample location  map, and associated spreadsheet files.  These documents, and a more detailed description of the project, are available below:

December 5, 2013 laboratory reports from Overburden Drilling Management, Ltd This is a PDF file. You will need Adobe Acrobat Reader to download it.

This laboratory reports from Overburden Drilling Management, Ltd, (ODM) documents total gold grain counts and magnetic/non-magnetic heavy mineral concentrate weights in 34 Rainy Lobe glacial sediment (till) samples that overlie an Archean greenstone belt in the Cook Area of Northern St. Louis County, Minnesota. These samples were collected on State-owned or State-administered mineral rights by Mn DNR in October, 2013. The approximately 200 square mile Cook Area is an area of historical gold and base mineral exploration, located in between areas of active gold exploration to the Northeast (Vermilion District) and West (Linden Grove Area). The Mn DNR has a contract with ODM to process the till samples that it collects.

Data table for 34 Phase 2 CATS samples with locations and normalized gold grain counts This link leads to an Excel document.
This data table provides locations as UTM coordinates and normalized gold grain counts (10kg sample weight) for the 34 samples identified in the ODM report.

Attribute data table for 139 CATS series samples This link leads to an Excel document.
This data table combines the field data and ODM results for the 34 samples collected in October 2013 with the results for the 105 Cook Area till samples collected in 2012 (see February, 2013 monthly data release.

Map of Cook Area sample locations and gold grain counts This is a PDF file. You will need Adobe Acrobat Reader to download it.
This map displays sample locations, normalized total and pristine gold grain counts and areas of active and historic mineral exploration, overlain on a 2010 aerial photograph of the Cook Area. Results from the previous phase of till sampling (105 samples) are also shown. The State of Minnesota has a dominant land position within this accessible greenstone terrane.

Next data release: Geochemical analyses

ODM-prepared representative splits of the silt and clay fraction (<63 micron), the non-magnetic HMC and magnetic HMC have been forwarded to Activation Laboratories (ActLabs) for geochemical analysis. The results will be posted as a separate data release.

Lode Gold in Minnesota

An explanation of lode gold in Minnesota and what makes it difficult to find.

More Gold Reports for Minnesota (Project 392)


DNR Open-File Project 392: Regional Survey of Gold in Till, Cook Area, St. Louis County

Map of gold deposits of gold in Cook County, MN

Map of gold deposits of gold in Cook County, MN

PDF of the image above

Normalized Grain Count Data With Locations

Lab Analysis with locations

The DNR is conducting a regional survey of gold in till in the Cook Area of St. Louis County. In this region, an Archean granite-greenstone terrane is overlain by relatively thin layers of Rainy Lobe till and other glacially-derived sediments. In comparable portions of the Archean Superior Province, the quantity and morphology of gold grains within samples of glacial till has led to the identification of associated bedrock gold deposits.

The results of this survey will support land management decisions in the region of high mineral potential, and may provide useful guidance for private mineral exploration companies that are considering gold exploration programs on State lands.

Project Manager: Don Elsenheimer

Basic Geology Stuff You May Want to Know

The first thing we will talk about is mohs hardness scale. This is something all geology 101 students are forced to memorize. It can help us prospect because we will know what minerals are likely to survive where we are looking.

Mohs Scale of Gemstone Hardness

Mohs Scale of Gemstone Hardness

The following are the typical field tests. It is not uncommon to see a geologist carrying a few of these items specifically for the following tests.

  • 1 — Soft, greasy, flakes of fingers (talc)
  • 2 — Can be scratched by a fingernail (gypsum)
  • 3 — Can be cut easily with a knife or a nail, scratched by a penny (calcite)
  • 4 — Can be scratched easily by a knife (fluorite)
  • 5 — Can be scratched by a knife with difficulty (apatite)
  • 6 — Can be scratched by a steel file (orthoclase)
  • 7 — Scratches a steel file (quartz)
  • 8 — Scratches quartz (topaz)
  • 9 — Scratches anything lower on the scale (corundum)
  • 10 — Scratches anything lower on the scale (diamond)

Most of us prospect in streams or areas that have seen water flow so we need to be aware of how minerals have interacted up to the point where we find them.

Blond sand is mostly made up of quarts with minor amounts of Feldspars and other minerals. (Feldspars tend to turn into clays minerals over time)

In general we can say that anything that does not have a hardness of 7 or greater is going to get beat up relatively fast because sand grains will slowly eat away anything softer.

Anything softer than sand grains will end up being smaller than the sand grains that surround them. If a mineral is harder than quarts it will likely stand up to the punishment, but it will also become rounded. It is difficult to tell the difference between rounded diamond, corundum, and topaz.
A later post will describe methods you can use at home to tell the difference.

So unless you are after load deposits you should realize that you are probably going to be looking for an elemental metal or something harder than quarts.

The information above seems like enough for now.

Note: I will be adding links to the other posts once I write them. This information is not meant to be complete alone.

V2 of the gold map

Made some changes to “the gold map”

More public data for MN, WI, MI regarding historic gold locations.

There were also a handful of updates provided by the MN prospectors. (Thank You)

Gold in Minnesota

Added some information on how to find gold in Minnesota.  The post covers the history of gold discoveries in and explains the most recent glacial advances.  In general sediments from the “Rainy” lob contain the most gold bearing sediment.

Click on the title of this post to see the full article.

Calendar updates

I have made lots of updates to the calendar.  Please let me know if you see any errors.

I will try to add special events over the next week or so.

MN sub site.

I have been adding material to MN sub site.

Please let me know what you think on the forum

Gold Map

Version 1 of the Upper Midwest gold map is now online. Most of our first reports came from the Twin Cities gold prospectors so the map is bias in that area. If you have additional locations where you have found gold please let us know on this thread.

The map will eventually provide prospectors in our region a good start at finding places to look for gold.

The image overlays that only visible in google earth will provide a good starting point for members in Minnesota and Michigan.  More information will be added in subsequent versions of the map.

The UMW Gold Prospecting website is a new information tool for an area not well know for gold and a place for persons interested in the hobby to share information and questions. Thanks for stopping by and hope to hear from like minded people in this great outdoor adventure.