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Posted (edited)

Hi guys, this is my first time posting here, i recently moved onto a property in north central idaho about 30 miles north west of elk city… anyway the property has about a dozen or so underground workings ,adits, shafts, and drifts etc…The primary producing mines on the property were the dewey, the evergreen, and the st.patrick… theres about 6 or more also unnamed mines on the property, the usgs page on the dewey shows that the mines produced copper, gold, and silver . Although my understanding talking to people around here is that gold was the primary target, but maybe they just really wanted a copper mine to be a gold mine idk? Im fairly new to this field and i cannot for the life of me find any visible gold on the property, i find lots of ore bodies with pryite and chalcopyrite, and more recently i found a vein of copper oxide. i know pyrite and chaclopyrite can carry small amounts of trace gold but would these be the type of ores the old timers would have targeted? Ill post some pics of some rocks ive pulled out of the mines, im hoping someone can point me in the right direction to actually find some gold… note: im not doing this for any monetary purpose, i have a day job and i like it, i just enjoy getting out , learning about the geology and digging a little and i think it would be fun to produce a little gold button from ore… i have a basic understanding of most mining processes and have the capabilities of performing a fire assay here… 

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Edited by HMM
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Great looking stuff!

And welcome aboard.

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Posted (edited)

You need to do further research to find out the type and size of gold the mines produced. Was any placer gold found on the property?

It's very possible it was all microscopic in nature and you'll have a hard time trying to recover it.

On the other hand if it was larger gold in veins you should be able to recover it using a metal detector? Are there any tailing piles on the property? If so, those might be your best bet. 

I'll be honest and say it doesn't sound promising. 

Edited by Morlock
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Thanks for the reply, from what i understand the gold on the property was all in the form of hard rock, not much in the way of  placer gold. I have found small gold in the river in the front yard, but nothing in the creek on the property that runs right in front of the mines.  From the usgs page on the dewey mine it sounds like they were finding free mill gold in small quarts veins. 

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You may have this already but if not Google, "History of the Dewey Mine"

"Good assays and free gold are reported to have been obtained from the Dewey, which was the main prospect worked at the time of visit. The developments chiefly consisted of a 50-foot tunnel. Anderson (1930, p. 36) described the geology at the mine as follows: In general the values in gold are low, about $2 to the ton, but there are some rich high grade seams. Mineralization has been extensive and the deposits, although of low grade, are large. The property has three or four parallel veins or mineralized zones, trending about N. 10º E. and dipping 75º S.E., the principal being the Evergreen, the Dewey, and the St. Patrick"

Free gold is the key term in the above paragraph. Free milling gold and visible gold are also terms to look out for when doing mine research. 

Keep in mind that it is fairly common for mineralized zones to include gold, silver and copper deposits. A lot of gold has been recovered from mines that were considered copper deposits. If you are interested in learning more about prospecting and metal detecting and other forms of gold recovery, use the search box (top right of forum page)to explore member posts and topics. And even if you don't see visible gold in your ore sample, that doesn't mean there isn't any free gold that may have eroded out of the host rock and be recoverable from the drainages' around (below), the mine adit. As Morlock alluded to, if you see any tailing piles, that usually would be a place to check for overlooked  specimens. (a metal detector generally is the tool of choice to expedite the search, along with a good loupe) 

 

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Don't let the fact that there is no history or mention of placer gold at the location of a hardrock mine stop you from searching for shallow gold nuggets in the drainages and bedrock areas around a mine. Hardrock miners often didn't pay much attention to areas away from the main lode.

 Years of erosion after a mine, "played out" has been known to uncover parallel veins or overlooked, isolated little pockets and patches around hardrock mines. 

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BMc thanks for the response, i just read that article it was interesting, so when that assay was done in 1913 gold was at 20/oz, so if the average gold per ton was $5 ton then 1/4 oz per ton was the average gold right? I dont think thats going to be visible gold in that case? That being said they said lower in the article  that  some high grade seams assayed at 5oz/ton, i would suspect that if i could find those high grade seams and chutes that i would be able to see visible gold in that quality of ore, but my main question is, what does it sound like the gold bearing ore looked like, was it the pyritic ore in quartz i find or was it in the white quarts which i also find in the adits? Or something else like an iron stained ore? Thanks for you're help!

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here are some rocks i commonly find in and around the mines, many of these were broken apart with a hammer first, they often look iron stained and brown sometimes black when you find them in the dumps before breaking them apart.
 

The first sample rock looks like an iron stained quarts under a microscope, i found it in a narrow vein about 4” wide at the portal of a caved in mine… i dont see any visible mineralization less the iron staining.

 

the 2nd sample is what i find the most of in the mines and in the dumps, its a grayish silver colored ore with lots of quartz and pyrite, sometimes it has chalcopyrite. 

 

the 3rd sample is a vuggy qaurtz vein i  discovered that is in between the lowest mine and the next one up, it runs in the same direction as the other veins in the mines and is very close to the lowest mines contact point boundry just higher on the hill, it has dark green and brown mineralization in some parts intermingled with the quartz.

 

I pulled the 4th sample out from inside an adit on the ceiling, i cant make out whats the hanging wall , the foot wall or the vein in this mine, ill post pics up soon, maybe tomorrow. Theres just random sections of quartz and pyrite ore all over the place in this one.

 

the 5th is like the 4th less the quartz banding, it has lots of visible pyrite in it

 

the last pic is from the footwall at the lowest mine, i suspect its some type of altered greenstone, its very dense and heavy and its hard to break apart, im not sure if that stuff in it is pyrite or not, it has the color of pyrite but it lays very flat on the rock and doesnt look like the rest of the pyrite i find on the property which is more crystal for lack of a better word

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Posted (edited)

I doubt you could find free gold in the amount of 1/4 ounce per ton.  When I hear free gold in hard rock, I think of a stamp mill.

That’s like taking a thimble of sugar sized grains of gold or powdered sugar and mixing it with 35 buckets of sand an hoping the golf ball sized rock that you crushed up had a sample.   I have seen rock crushers for sale at gold shows, but to me, they don’t look like the type of equipment that could crush the amount of dirt for an operation, but perhaps it could crush enough dirt for a better sample.

Placer mining is a bit easier.  You can get a bigger sample like a pan to a bucket of dirt and pan that to see how much is in there with an 85% to 90% recovery rate.

As far as getting stuff off google, in my area, I have not found anything that would help me at all in finding gold.  I already know its a gold bearing area.  It’s also whatever reports the company decided to release at the time that have been digitized for us to find.  I’ve been on dozens of prospecting trips where I reasearched these online downloads for hundreds of hours but have not been able to find any placer deposit worth working big time.  In fact, I found some data that makes me think quite a few of the placer mines that were created were made so that someone could get land from the government to live on.  There’s amazingly little workings on these sites for a hard rock mine patented mine.  Not always the case; there is the Vulture mine locally, but that is an exception not a rule.

The green stained rocks you showed earlier look like a copper ore, perhaps chyrsocolla.  100 years ago, copper deposits could be worked by taking that green ore out of the ground and putting it on donkeys.  Today that copper ore needs to be strip mined with large dump trucks or some bettery samples put up for sale on Etsy or E-bay.

The black staining is something I’m told that locally black staining in quarts like that is mineral deposits that tend to contain gold. Actually, when I have crushed samples with this black staining or looked at them with a 60X loupe, I have never found free gold in them.  I have only found a spec or two in some white quartz samples, which goes against everything the old timers told me.  I also notice that the metal detecting pics tend to be lodged in white quartz and not the black stained quartz.  I think I’ve seen one or two pics gold nuggets hosted in the black ugly quartz on threads onthis forum.

Edited by chrisski
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Looks like you have a lot to work with, but without more research, (including a geologists report), that hopefully would identify the host rock that the gold was found in, I'm afraid it would be gross speculation to try and answer your questions with any degree of certainty. Gold can be found in a variety of rock types and low grade and complex ore deposits may require geochemical or other types of analytical processes to reach any informed decision that might be helpful. I would search the internet for additional reports through your state bureau of mines, USGS, claim and ownership records etc. The information is probably there somewhere if you want to go to the trouble of digging it out.

You might try crushing some of your ore samples and pan out the fines to see what you come up with. If you had a good, highly sensitive metal detector that could detect small gold, you could pass your ore samples over the detector coil and possibly determine which ones to crush or might be worthy of further examination. Good luck with whatever you decide.

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Posted (edited)

History of the Dewey Mine

Idaho Geological Survey Staff Reports (S): S-07-5

The darker rock very much looks like several low grade silver/lead ores I've seen. "Free milling" is a statement about the chemical state of the gold and doesn't in any way indicate the actual size of the gold. In most mines hard rock gold is not found in a form that's visible to the naked eye. Trying to pan for invisible gold tends to yield no visible results. Nothing wrong with trying but the lack of panable gold doesn't indicate no gold - just gold that can't be successfully panned.

The copper/iron are typical of the deposit type. The last picture with the pyrite looks like it may be arsenopyrite. Ot's quite likely the hard rock you ran into is greenstone.

It looks like it was a fairly productive mine that relied on inexpensive mining and good metal prices. There are a lot of these type mines still out there but with development times today of 7-12 years or more and a metals cycle of less than 10 years they rarely succeed in producing a consistent profit over time.

Thanks for sharing. Always good to see someone else's rocks.

Edited by clay
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Thanks for the reply unfortunately there are two mines named the dewey, mine is in idaho county the other is in valley, we are at 1800 ft ish the other is at 7500 plus.

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Thanks for the insight clay, does anyone know what this brown powder that i found in these envelopes might be, they were addressed to the previous property owner under the name of the mine?

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4 hours ago, HMM said:

Thanks for the insight clay, does anyone know what this brown powder that i found in these envelopes might be, they were addressed to the previous property owner under the name of the mine?

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I can't tell you what the brown powder is, but I did a little searching about ASARCO, they were founded/incorporated in 1899 as the American Smelting And Refining Company, they have several refining operations across the USA as well as others around the world, each specializes in smelting or refining different types of non-ferrous metals, at present the one they have in East Helena Montana is a "Lead smelter", so that may have something to do with what the powder is unless that location was doing other types of metal when the package was sent out.

https://www.company-histories.com/ASARCO-INCORPORATED-Company-History.html

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6 hours ago, HMM said:

Thanks for the insight clay, does anyone know what this brown powder that i found in these envelopes might be, they were addressed to the previous property owner under the name of the mine?

You are welcome HMM.

What you have in the envelope is crushed and mixed ore. It's important that it was kept sealed and has a tracking system for the sample. There is probably another entry on the mining companies records showing where the sample was taken from - information the assayer should not know.

When you send an ore sample in for assay usually you will send several ounces to several pounds of ore. The assayer will crush and mix the powdered ore and then take a small sample for fire assay. The person ordering the assay can request the rest of the sample be returned to them. Often these samples were then sent to other assayers. Even today this is common practice and practically required for any mining company selling mining stock or under SEC control.

Often these assay samples are provided to significant mineral rights owners as proof of the basis for smelter receipts. Assays and smelter receipts in the mining business are the only real way to know how the ore is running. Assays audit the smelter receipts and visa versa.

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