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Hello all, found this speci. from a gold/siver mine in Summit co. Colorado. I initially thought it might be arsenopyrite, but now beleive it is Galena due to the fact (among other things) it is extreamly heavy!

After reading a report from 1909 on this mine, it says the high grade ore came from the Galena.

My question is how to determine if the sample is agentiferous or auriferous without doing a fire assay. I dont want to sacrifice the whole peice to find out. Any ideas?? Here are the pics. They are as close as I could get w/ my camera> Thanks ....Luke

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post-25428-0-33234300-1307848833_thumb.j

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Luke most likely is primarily galena with some silver. These minerals commonly mix. I have some with quartz that I cabbed with lapidary equipment. The galena is really soft. You would have to assay it to see if there is any gold unless it is visible to the naked eye. Jerry

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Hi Luke,

Being that heavy, it could also be calaverite, which has gold and silver in it. I have seen specimens (from Colorado)that look a lot like your sample.

Ben

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Hello all, found this speci. from a gold/siver mine in Summit co. Colorado. I initially thought it might be arsenopyrite, but now beleive it is Galena due to the fact (among other things) it is extreamly heavy!

After reading a report from 1909 on this mine, it says the high grade ore came from the Galena.

My question is how to determine if the sample is agentiferous or auriferous without doing a fire assay. I dont want to sacrifice the whole peice to find out. Any ideas?? Here are the pics. They are as close as I could get w/ my camera> Thanks ....Luke

My guess is galena also since it's very common. Unless you have a lot more of it, there's probably no way you can test it without destroying it. I think calverite has a different colored streak then galena.

Steve

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Hello again, and thanks for the reply's. The mineral is most certainly Galena, streak is dark grey, as well as its heft give it away. I'm just wondering whether or not you can do a test such as a specific gravity test or ??? to determine if there could be either gold or silver in the piece? I do have a small piece, about 1"x1" that I could have assayed if that is a large enough peice? (not sure).

I was also wondering if there is a way to disolve the host rock while not damaging the ore?

Ps. I'm not going to be doing any hard rock mining at this location, I'm just curious as to the composition of the ore.

Thanks again Luke!

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Hi Luke-

I don't think you'll find enough gold or silver in it to make that much difference in the specific gravity on that small of a specimen.

I just recalled (conveniently )there is an analysis that requires only a pinhead sized piece of ore but it's kind of expensive- $50.00 or more.

Yes- there's an acid which may dissolve your host rock but you don't want to use it for that purpose.

Steve

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Yes Looks like Galena for sure.

Can have some minor gold content, up to 1 or more % silver.

Knock a little peace off and hit it with Red Devil lye/hot water. Lead will boil away.

Put a Drop of SelSun Blue shampoo on a spot.

If it turns a cool Cobalt Blue, it has some good Silver in it.

LOL! I love Bathroom Chemistry.

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  • 2 weeks later...

That is a nice little sample for the collection.

Paul

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Just a follow up, had a assay done and the galena ore sample, it ran 74 oz. per ton silver and .034 oz gold. so pretty rich in silver. Neat little peice to add to the collection.

Don't you wish you could find a vein like that?

Steve

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Don't you wish you could find a vein like that?

Steve

You would have to ship that ore all the way to Canada to smelt it. Unless it is silaceous ore it is virtually worthless and even then it needs to be 200 OPT and 60% silica to be marketable. With tons of galena laying in piles here that runs 250 OPT or more no one yet has figured out a way to make a profit from it. While a favorable fire assay is a neat thing to look at the real story is in the amount of lead, cadmium, boron, bismuth etc.etc.

There are ledges of pure cubic galena here that are three feet thick. They run in the hundreds of ounces per ton when the entire cross section of drift is considered. Unless you have a flux mine and can guarantee shipments of 100 tons or more no smelter in the US will consider it.

I know a couple of small operations that smelt their own crude dore and then sell that to a refiner. That is the only way that American silver ore is marketable at all unless you have a giant operation and can keep a smelter busy three shifts a day. And then you must find a smelter that deals in lead based, low silica ores and that means shipping the entire mess to Canada.

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(Bedrock bob quote)

"There are ledges of pure cubic galena here that are three feet thick."

I just saw a nice cubic Galena cabinet specimen sell for $11,000 in a natural history auction! Might be worth taking the TLC up there to check it out.

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You would have to ship that ore all the way to Canada to smelt it. Unless it is silaceous ore it is virtually worthless and even then it needs to be 200 OPT and 60% silica to be marketable. With tons of galena laying in piles here that runs 250 OPT or more no one yet has figured out a way to make a profit from it. While a favorable fire assay is a neat thing to look at the real story is in the amount of lead, cadmium, boron, bismuth etc.etc.

There are ledges of pure cubic galena here that are three feet thick. They run in the hundreds of ounces per ton when the entire cross section of drift is considered. Unless you have a flux mine and can guarantee shipments of 100 tons or more no smelter in the US will consider it.

I know a couple of small operations that smelt their own crude dore and then sell that to a refiner. That is the only way that American silver ore is marketable at all unless you have a giant operation and can keep a smelter busy three shifts a day. And then you must find a smelter that deals in lead based, low silica ores and that means shipping the entire mess to Canada.

Regardless - it would still be nice find even if you couldn't profit off it right away. I would hold it in hopes things might change in the future.

Steve

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  • 2 weeks later...

That's great you got some precious metals in it! One trick I have been told by geologists when I worked at a silver mine (Lucky Friday, ID) is that argentiferous galena will have bulged faces. Apparently a silver atom can be subsituted in the galena lattice and so it manifests its presence as a slightly bulged surface of the usually flat cube faces.

It would be intresting if you can confirm that in your specimen by using a handlens...

I'd be really interested in learning what you find out if you try it out...

Happy collecting,

Mark B.

Vail, AZ

P.S. I thought I'd google it and found this: http://www.dmme.virginia.gov/commercedocs/PUB_89.pdf

Open that PDF and search for "bulging"

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