Just got back from northern Nevada..nok gold, but....

[Jim in Idaho]

I was down in northern Nevada this week for some nugget hunting. All I found were two large, what appears to be, copper nuggets. But, the interior color is more silvery, or gray, than copper-colored. The nuggets I found last fall down there looked like a bright penny on the interior. These two have a black skin on the outside, and when filed away it shows a metallic gray. No attraction to a super magnet. They were both down about 10", and the small one was under a large rock. They were about 300 yards apart in the same drywash. The exposed metal leaves a coppery streak. The black skin leaves a dark gray, or nearly black streak. No way to get a specific gravity...my gem scale doesn't go high enough. Appreciate any help.
The big one weighs 100 grams on a cheapo food scale. The small one weighs 71 grams.

Jim

 

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[Clay Diggins]

Cuprite an ore of copper streaks metallic red - brown.

Although Cuprite is dark red it often looks black or dark brown. Look with good magnification for dark red crystals in the matrix.

"Cuprite is commonly found as an oxidation product of copper sulphides in the upper zones of veins, often associated with Native Copper, Malachite, Azurite, Limonite and Chalcocite."

Heavy Pans

 

[Jim in Idaho]

Cuprite an ore of copper streaks metallic red - brown.

Although Cuprite is dark red it often looks black or dark brown. Look with good magnification for dark red crystals in the matrix.

"Cuprite is commonly found as an oxidation product of copper sulphides in the upper zones of veins, often associated with Native Copper, Malachite, Azurite, Limonite and Chalcocite."

Heavy Pans

I've been all over these with a USB microscope, Barry. If there are red crystals, I can't find them. I just ran over them with the DFX. It shows 16-28. A wheat penny reads 83.
Jim

 

[Clay Diggins]

I wouldn't expect it to read the same as native copper or a penny Jim. It seems it's probably a fully oxidized stable mineral of copper (Cu2O).

Try over at Chris Ralph's site. He has a specimen there that closely resembles your find. He also outlines several tests for Cuprite.

You can see an interactive map of known Cuprite localities in Nevada. Maybe your find was in a known locality.

Whatever it is it's clearly a copper ore.

Heavy Pans

 

[Jim in Idaho]

Looks like there was no cuprite found where I found these. I agree about it being copper ore. I'm starting to think it's a copper/nickel alloy.
Jim

 

[gold tramp]

Looks like there was no cuprite found where I found these. I agree about it being copper ore. I'm starting to think it's a copper/nickel alloy.
Jim

Crack in two let's see inside. Get a better idea.
Gt ..

 

[Clay Diggins]

There is some nickel in the Ely copper ores. That's in the form of Pentlandite. I doubt that's what you have though because of the Azurite and Malachite progression on the surface. Not really compatible with a nickel/copper ore.

Does the specimen conduct electricity?

Heavy Pans

 

[Jim in Idaho]

Yup...I'd never have detected it otherwise. The resistance varies from 1.4 megs over 1/4" to 2.5 over an inch. Some places 1.5 over an inch. No question conductive. it's metal.
Jim

 

[Jim in Idaho]

I just put a small piece of ice on it....had water running off in 30 seconds, and the specimen got cold, fast.
Jim

 

[Jim in Idaho]

I cut off a small piece to do an SG test. You can see the copper floating in the other metal.
Jim

 

[Jim in Idaho]

SG=5.55

 

[mike(swWash)]

Very cool looking specimen.

 

[OwenT]

Interesting. It's too bad you didn't find any gold. Stories make it seem like the nuggets just about jump right into your pocket in Northern Nevada. I'm just curious about how likely someone is to spend a whole week there and not find a few pieces (assuming a competent operator and a decent amount of research).

 

[Jim in Idaho]

Owen, it just isn't that simple. Probably was at some point in time, but not now. Also, I'm more of a prospector than a nugget hunter, so I go places where not a lot of gold was found in the past. I enjoy the challenge, and would rather find something of significant value than a few dollars in nuggets. You have to just enjoy being out there. If you only go because the gold may show up, you're wasting your time IMHO. For me, any gold is just icing on the cake.
Jim

 

[Lanny in AB]

Jim, no chance there's some silver in your pieces?

Regardless, enjoying the back and forth that's generating interesting geological facts on this thread.

All the best,

Lanny

 

[Jim in Idaho]

OK, guys. The XRF gun said it's 96% copper. A bit over 1% lead. 1/2% nickel about 1% Tin 1% iron 1%manganese If they add up to more than 100% it's because I'm approximating. There was some other trace stuff. I expected the copper to be lower.

 

[Lanny in AB]

Thanks for the specifics in your update. That's a really interesting find you made, a bit of a mystery as to how it looked as well.

All the best,

Lanny

 

[Clay Diggins]

OK, guys. The XRF gun said it's 96% copper. A bit over 1% lead. 1/2% nickel about 1% Tin 1% iron 1%manganese If they add up to more than 100% it's because I'm approximating. There was some other trace stuff. I expected the copper to be lower.

Sounds like it might be a natural copper nugget Jim. They can be very high percentage copper in some areas.

Curious that the XRF operator didn't include SiO2 or S. Usually you would want to test for Silicon and Sulfur at the least when assessing metal ores. I suspect a lot of that copper is still bound up in Sulfur compounds.

Thanks for keeping us updated.

Heavy Pans

 

[Jim in Idaho]

Barry, the guy took time from his daily work to do the test, and ran it twice. I didn't think I should be too demanding about what he did. I understand what you're saying, but it was a freebie...LOL. Hard to believe these might be natural. Definitely going to go back, and do some more poking around in there. Wish I could afford one of those TEM/TDEM units to get greater depth on the possible lode. For now, the TM808 will have to do. May not get back down there until the weather cools off this fall...it's going to get hot next week. I appreciate your insights on this thread.
Jim

 

[Jim in Idaho]

Just got the assay results back. I'm attaching the .PDF
Jim
View attachment J Nelson 7.7.2020.PDF