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Underburden

Blood Nuggets

18 posts in this topic

Got quite a few pieces of gold with host rock still attached this summer.

Sold the lot to a friend of mine and he sent me some close up pics.

I copied them to a black background.

Anyone know what the red mineral is?

Thx

Bob

red%2Bnugs%2B1.jpgred%2Bnugs%2B2.jpg

 

irjus likes this

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It's hard to say what it is without some more info, e.g., streak color, hardness,, it would be hard to check other properties because of the size, the gold and not wanting to damage the specimens greatly, but those two test should be doable, which would help more than just guessing what type of "red rock/mineral" it could be. 

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Bob,

 

The reddish colored material looks similar to the dumortierite deposits near Oreana, Nevada.  Don't think it's likely that's what it really is though and I'm just a rockhound,not a geologist.  Hope you can take it to someone and get a positive ID on it and let us know.  From your pictures it ranks up there with the most striking specimen gold I've seen.

 

Thanks,

 

Bob

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Chris sounded pretty positive... I'll go with his answer.

From here it looks like the mystery mineral is thick and solid, with the gold embedded in it.  Hard to tell from a picture but it doesn't look like a thin coating like Chris suggested.  From long experience working with geologists, I know that whenever a geologist makes a statement with 100% certainty, it's 50-50 he/she is wrong and if two geologists agree (rarely happens) the odds for them both being wrong go to 10-1.  (just kidding Chris and any other geologists here)  Hope Bob Underburden can get a positive ID on it and let us know.

 

Bob

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I forwarded the nugget images to one of my geologist mining partners and here's his view, of course based only on looking at the pictures:

 

"I want those nuggets!  I guess the implication of the "thin coating of hematite" is that beneath a mere film of the troublesome stuff, there's solid gold!

However, from a quick look at the images, I'd say that the reddish (to pinkish and purplish and translucent locally) material is basically matrix, now oxidized, with which the gold was co-precipitated.  In this matrix, one can see earthy reddish to submetallic purplish hematite and almost certainly quartz (the translucent material).  My guess would be that the gold was precipitated initially with quartz and a metallic sulfide, and then the sulfide (I'd suspect chalcocite replacing chalcopyrite) was thoroughly oxidized to hematite.  There probably are local areas in the specimens in which, serendipitously, a thin film of earthy hematite conceals underlying gold.  However, my opinion (from the pictures alone) is that gold and the hematite-quartz matrix are present in about equal proportions."

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All good guesses!

 

So, the only way to "know" is to take the gold to someone that has an X-ray Fluorescence Spectrometer (XRF) and get a printout of the elements.

 

The results will be conclusive and provide important insight to the possible source of the gold.

 

It's elemental! :)

 

- Geowizard

How much would an XRF analysis cost for something like Underburden Bob's nuggets?

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When I try to get things done at no cost I sometimes end up getting charged double. :)

 

Not sure if Underburden Bob would be willing to send a sample to someone in Nevada, but I'll check around here and see what kind of responses I get.  Worst case I'll learn something.  I understand that the XRF analysis requires that the material be powdered, so Bob would lose a specimen or part of one?

 

Also, it seems to me like a basic hardness and density test would tell something.  Those could for sure be done for free.

 

- Bob

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Underburden Bob,

 

So far I've discovered that the Nevada Bureau of Mines and Geology's analytical lab has been closed due to budget cuts.  There are other labs here but I'm wondering if you want me to  pursue this any further?

 

- Bob

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I have full confidence in the response from Reno Chris. 

An old salt who has been mining this same area for years gave the same response as Chris.

I see no need to go further...if it walks like a duck and quacks like a duck, it's a duck.

B)

Bob

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