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Michigan Silver/Copper

Posted by Stephen Rose  
avatar Michigan Silver/Copper
May 22, 2012 12:24AM
I have had this for a while and know that it was in a collection in 1940 and that it is from the Keweenaw Peninsula but can only guess at the mine location. It badly needs cleaning and perhaps some careful abrasive work on the back to better expose the silver crystals. Overall size: 8x8x6 cm. Silver crystals 'fan': 6.5x4x5 cm. Largest silver crystal is 1.5 cm long.


Front view


Back view




Thanks for your input!

Cheers,

Steve



Edited 1 time(s). Last edit at 05/22/2012 03:00PM by Stephen Rose.
Re: Michigan Silver/Copper
May 22, 2012 04:18AM
Very interesting piece. The silver is very interesting.
avatar Re: Michigan Silver/Copper
May 23, 2012 08:17PM
Keith,

I have seen specimens that look a bit like it, from the Kearsarge mine for example, but most do not have crystals so well defined as on this piece. I am hoping some of the Mindaters more familiar with the Michigan specimens will chime in here, perhaps with information on possible location if not value.

Cheers!

Steve
avatar Re: Michigan Silver/Copper
May 23, 2012 09:07PM
Specimen is probably worth two to three thousand dollars. With fine specimens selling for what seem to be such amazing prices these days, I hope I am not under valuing the specimen.

Rock Currier
Crystals not pistols.
avatar Re: Michigan Silver/Copper
May 24, 2012 02:18AM
Rock,

Interestingly, your high estimate is just about the annualized rate of inflation for value of this specimen for the past 35 years! Richard Kosnar appraised this piece in 1977 and gave it a value of $700-$750. $750 from 1977 to 2012 at an average annual rate of 3.95% inflation comes to $2,908.14. I am pretty conservative about prices but would feel that as the better specimens have out-performed inflation that the 3K area is probably a lower value.

I have found nothing really similar to compare it to, but one that was somewhat close apparently sold for over $30,000. That would be a case of the "such amazing prices" that you refer to and I am comfortable knowing that we aren't talking those numbers here.

Thanks for the input!

Cheers,

Steve
avatar Re: Michigan Silver/Copper
May 24, 2012 05:34AM
Steve, here are a couple from my collection.

Silver on Copper, Michigan©

Silver on Copper, Michigan©

Silver on Calcite, Norway©

The first two are before cleaning. I don't need an evaluation. There are others.

Rock Currier
Crystals not pistols.
Re: Michigan Silver/Copper
May 24, 2012 02:25PM
Stephen,

The crystal form reminds me of something I've seen at the A. E. Seaman Mineral Museum in Houghton, MI. I'll look through my photo collection tonight and see if I can't jog that memory.

Keith
avatar Re: Michigan Silver/Copper
May 24, 2012 03:58PM
Beautiful specimens, Rock. Thanks for posting them. The Kongsberg piece is particularly striking.

Keith, thanks for checking. I will look forward to hearing about what you find.

Cheers!

Steve
Re: Michigan Silver/Copper
May 25, 2012 02:12AM
Here is the silver piece I was thinking of earlier. It's from the Cliff Mine, Keweenaw Co., MI and unfortunately, I did not take any measurements when I took the photo. However, the crystal structure looks quite similar to yours.
Attachments:
open | download - Silver Cliff Mine.jpg (48.4 KB)
avatar Re: Michigan Silver/Copper
May 25, 2012 02:33AM
Keith,

That is a lovely specimen!

I do see what you mean about the crystal structure. Thanks for looking it up and posting.

Cheers!

Steve
Re: Michigan Silver/Copper
May 25, 2012 08:53PM
It's a cool piece, but it doesn't have anywhere near the kind of pop you'd expect to bring 30k kind of numbers. A lovely piece for fans of the wonderful old classics, and a neat combo for the element lovers. Two grand would be most reasonable to my mind; maybe cleaned up a bit, to show some contrast, on a fancy acrylic stand, at a big show, closer to 4k, on a good day.
avatar Re: Michigan Silver/Copper
May 30, 2012 06:04PM
Tim,

Thanks for the input. The piece that I referenced as having sold for over 30K had some similarities to mine, but, as I said, I am comfortable knowing that we are not talking about those sort of numbers here.

Cheers!

Steve
avatar Re: Michigan Silver/Copper
June 01, 2012 02:00AM
Stephen,
That is a great classic Keweenaw specimen! If I had to guess based on crystal form, I would say one of the Keweenaw fissure mines (Cliff, Phoenix, St. Clair, etc...) would be a likely choice. It really doesn't look like a Kearsarge/Pewabic Lode specimen. I'm trying to see some matrix but I don't see too much; that would be a helpful indicator.

Keith,
The Cliff specimen in the Museum is about 10-12 cm tall.
avatar Re: Michigan Silver/Copper
June 01, 2012 07:49PM
Paul,

Thank you for your comments.

The specimen has an area of quartz embedded in the back of the spray of silver crystals and infilling the space between the silver crystals and some of the rough voids in the copper. The quartz is generally translucent to clear, and I can see no significant crystal faces. This is shown broad view in the second picture I posted originally and a bit more in detail in the first picture below.


Quartz infilling Ag/Cu matrix

At the base of the specimen is a thin patch of hard, granular material that coats or fills voids in the copper. This is fine-grained, grey to brownish with very small patches of other minerals of various colors that might be secondary Cu products and something like epidote. Within this material are a couple of openings with very small, well-formed, clear quartz crystals. Some of these have a greenish tinge of epidote color. The overall picture that comes to mind is a vfg fault gouge with some later silicification and quartz re-crystallization. The pictures below illustrate this as best my camera can.


Overview matrix


Detail matrix

Cheers!

Steve
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