Mass City, Ontonagon Co., MI

August 7, 2003



Caledonia Mine Portal



An ore car from the Caledonia Mine


I had visited the Caledonia two years ago, but decided to give it another try this year. This mine is being operated for specimens and collecting. They offered underground collecting as well as surface, but I opted for the surface collecting.


This mine is quite a ways south of where we were camped. Itís just past the Knowlton Mine, which I visited on Tuesday. The exact location is Lat. 46 deg. 45.064í, Lon. Ė89 deg. 07.215í. Although we had to park on the road and walk down into the dump, after the trip was over collectors were allowed to bring their vehicles down into the dump to haul out what they had collected.


Thereís a lot of calcite here, and most of the crystallized copper is under it. You donít know what you got ubtil you get it home and leach out the calcite with acid. Some people in the area recommend sulfamic acid, but I havenít had much luck with it. I prefer to use muriatic (hydrochloric) acid diluted about 1:1 with water. As long as you donít leave the specimens in the acid too long there isnít much danger of etching the copper. Iíve found that about 2 hours works well. Of course, you have to thoroughly rinse with water to remove all acid, and possibly neutralize with an ammonia rinse before drying the specimens.


In addition to the copper, thereís a lot of epidote, pumpellyite, quartz and saponite. The microcline (var. adularia) is the best Iíve seen in the copper country. In addition to the opaque orange-red crystals that are seen everywhere in the copper country, there are also delicate pink translucent crystals. Silver and datolite are also reported from here, but I didnít find any.


On to the next field trip: the LaSalle Mine


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