Copper Hunting on Michigan’s (UP) Keweenaw Peninsula

Tom, further to your question about detecting copper on Michigan’s Keweenaw Peninsula, I did a few quick checks.

A preliminary search reveals there are potentially more than 220 collecting sites connected to former minesites and related shafts on the Upper Peninsula. Do a search on “Michigan Copper Country” for example, and you bring up reams of information on everything from (a) search areas to (b) mineral collecting clubs to (c) overnight accommodations. Many of the collecting sites are privately owned and require permission to search.

Below is a link to the Copper Country Rock and Mineral Club, a highly visible, semi-professional level association that produces various articles and publications about the area. One example I have in hand is the “Mines and Minerals of the Lake Superior Copper District” published April, 2001. It provides at least 120 collecting sites, providing good information about other “collectable” minerals known to commonly occur at these sites. More detailed information is provided on an abbreviated list of sites regarding history, mineral production, and simplified road maps marking collecting locations. With some good topographical maps, a rock hunter would be primed and set. Here’s the link to the Rock and Mineral Club where plenty of information about searching the Upper Peninsula can be obtained…

http://www.ccrmc.info/

I have not spoken with my brother about the sites he visited last autumn, but now do recollect the Caledonia Mine after viewing the website. I believe it’s the only remaining active mine on the peninsula, a huge producer since the middle 1800s. A pay-to-mine service is available, I seem to recollect it was $100 per person per day. That may seem a bit expensive, but they supply each collector with their own individual ore pile. I suspect they “seed” those individual piles. The flip side of the costly fee is that you won’t need to return there to hunt more copper. Everyone he talked with departed the Caledonia with multiple good size copper nuggets/specimens. Here’s the link…

http://hunts-upguide.com/mass_city_m...onia_mine.html

The A.E. Seaman Mineral Museum also runs a mineral-collecting program for a reasonable fee, somewhere around $25 dollars to have access to three different collecting sites. Now this is based on recollection, but I think the program was called “Copper Country Mineral Retreat”. I have a contact name that was good August 2009 for more information…Darlene Comfort (906) 487-2437. Otherwise do a search, I’m sure you’ll get lots of information, this is a world class museum for minerals, associated with Michigan Tech University.

I had another look at some interesting copper mineral samples from the Michigan’s Upper Peninsula. Easy to see why collectors are interested. These samples are fascinating. They are beautiful native crystalline copper, almost looking iridescent in places. They are massive and rugged looking, with oodles of character. The only native copper photo I have available to post is hardly worth the effort since it does not do it any justice, but here it is…



Below are a few copper sulfide samples you may very well run into over on the Keweenaw Peninsula. They’re not great specimens by any stretch, but all I have at the moment. The first photo is chalcopyrite in a calcite matrix, the yellow metallic material on the viewers left-hand side of the rock



The next photo is bornite, the second stage in copper sulfide oxidation or enrichment. This material is well known as the “peacock ore”.



The next photo is of rock material covered in tiny crystals of covellite. Covellite represents the third stage in copper enrichment but is not found nearly so frequently as the other sulfides in my area. I have found larger crystals of covellite in company with native silver attached to calcite here in Ontario. Naturally exposed covellite will not have the brilliant metallic blue hue associated with freshly exposed surfaces exemplified in the specimen photo below. BTW, the final enrichment stage is chalcocite, gray/sooty colored, almost 80% copper by weight, but I have no specimen photo to post.



So, what type of unit should you use? If you visit the Caledonia, you can easily tear down your ore pile in three hours and detect it with just about any coin/relic unit. At other sites, consider that the targets you seek will be large, high conductive multi-lb samples that will generally fall into the screwcap-zinc penny to half-dollar conductive range. Second, the ground you will search has likely seen plenty of past detecting activity. So figure the remaining targets will be deep (especially in low mineral ground…easy pickings), whereas you will need a PI unit that can give you depth in higher mineral ground.

Now, I’d prefer to be on site prior to handing out advice for searching any given location. But let’s take a run at it anyway. I suggest that in low mineral ground, low or high iron trash levels, use a VLF unit like your MXT with the large 12” concentric coil. If trash is extreme in places, you can resort to the 6”X 10” DD to improve target separation. There is no reason why you can’t use your TDI with the large stock coil in mild, low trash ground, but with the large targets you seek, I would dig only the high conductive signals and that means operating with the GB turned on. Your TDI set to high conductives will avoid much trash and distracting small copper that falls into the low conductive range. Now, under low mineral/trash conditions if you want to go for any size copper nuggets/specimens, there is the option of turning off the GB and gaining some additional depth. It wouldn’t be my first choice, but definitely a viable alternative.

In high mineral ground with low trash levels, use the TDI with the stock 12” stock coil and set it to signal over high conductives if you’re looking for the big high conductive pieces only. Where iron trash is proliferate, my decision would be based on just how hard the area has been detected (ask around and look for signs of digging), and what kind of depth could be had with a VLF unit (do some testing). Over my high mineral ground that has been intensively detected for 40 years, all the VLF discrimination in the world won’t do you any good when you can’t get the necessary depth to reach the deeper targets. We know there are plenty of multi-lb targets beyond one and a half feet. So, the priority here is detection depth and that makes a PI unit with limited discrimination ability and a large coil the preferred choice, regardless of trash and pyrrhotite levels. You may have to dig larger iron in order to get the large, deeper copper samples in bad ground.

The TDI’s limited discrimination capability becomes even more important when searching high conductive copper at pay-to-mine operations if your time on the ore piles is restricted. In 2009 for example, the Caledonia Mine limited collectors to three hours per visit, so you stand to profit by using settings that make the best use of your time.

Could be that Steve will drop around and maybe give his view on what might be a good choice for searching high conductive copper in high mineral ground with high iron trash levels. Whatever he may suggest definitely works for me. Good luck with it Tom,

Jim.