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Free Mill Gold


Andyy

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Hey all.  I was wondering .. when you are researching areas with mines, how do you know if these mines have or had Free Mill gold? I have done some searches in USGS minedata but do not see how you know if it is free mill gold or not.  

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Hey Andy, we use several books by different authors to start off with. Then here we use some state ran Web sites. They give information on dang near every mineral producing mine in Nevada. I don't know if Arizona has the same kind of services or not. Of course there are areas that they don't list or dont have info on and we have to do our own looking into. But that's part of the fun right. Finding something that nobody else has found. Good luck

Dan

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I believe you need to expand your question / search, Andyy -- because I'm thinking you're seeking this info looking for mine dumps etc to detect..

If this is the case, and with the given that 'free milling (of Au)' is a gravity only recovery process and the known that mini-micro Au can be recovered this way, it seems to me knowing whether or not a mine contained free milling gold isn't enough information because I'd hazard the guess that at least some free milling gold can be found in even the most chemically-bound deposits..

Swamp

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Andy how they mined the gold there in a given area will tell you if it was free milling gold or sometimes bound up in sulfides and sometimes referred to as complex ore. AzNuggetBob

Edited by AzNuggetBob
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Andy...I would not let the fact that a mine was mining gold that was not free milling deter you from detecting the area.

Back in the 80s, Dad and I dredged up a 3 oz nugget and some smaller ones from a wash that ran past a mine, about 1/2 mile below it. The mine was crushing up pirite and processing it to get the gold. Luke found some flakes about 1/4 mile below the mine crevising.  So, my thought is, what may have been happening geologically at the mine site was completely different from what was happening a 1/2 mile away :) If its a mineralized area...BEEP IT!

Tom H.

 

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27 minutes ago, TomH said:

Andy...I would not let the fact that a mine was mining gold that was not free milling deter you from detecting the area.

Back in the 80s, Dad and I dredged up a 3 oz nugget and some smaller ones from a wash that ran past a mine, about 1/2 mile below it. The mine was crushing up pirite and processing it to get the gold. Luke found some flakes about 1/4 mile below the mine crevising.  So, my thought is, what may have been happening geologically at the mine site was completely different from what was happening a 1/2 mile away :) If its a mineralized area...BEEP IT!

Tom H.

 

So True. Its amazing how much things can change in a  1/4-half mile. AzNuggetBob

Edited by AzNuggetBob
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I found galena nuggets under a vein outcrop on one side of a ridge and as the vein passed over the ridge and into a different host rock zone it started producing gold nuggets. Ya I learned a lot. AzNuggetBob

Edited by AzNuggetBob
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Same here. One of the highbanker spots we have here is funny. On the side we're on is nice chunky, pure gold and on the other side of the ridge it is all disseminated gold locked up in the sulfide. The ridge is the cut-off point. We have dug down to the bedrock and tested all of the bench material on that side and not a speck. I found this place by reading the many books I have for nevada. Come to find out, the info in the book was dead on about the type of gold in this area. Them old timers that wrote them books were pretty accurate with their description and info for the different mining districs. Very good source of information. 

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Yeah, I think I need to rephrase my question,  like what Swamp said.  Let's say the goal is strictly hunting for specimens in tailing piles.   Last thing I want is to beep tailing piles where the gold is not detectable.  I am more interested in the research aspect of things.   To be specific, what sites do you use to investigate these mines (ex. USGS ..) and what key information are you looking for within these documents to tell you that there might be detectable gold.   Keep in mind that my location is Arizona.  :) 

 

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All productive states have a site someone like this one I think. Takes a bit of digging around but everything your looking for can be had. https://geoinfo.nmt.edu/resources/minerals/mines_database.html

 

 

 

Edited by homefire
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28 minutes ago, Andyy said:

Yeah, I think I need to rephrase my question...

Andyy -- when you went to USGS did you go to the pubs section..?
If not, give pubs.usgs.gov or pubs.er.usgs.gov a try..

And what Homie said too..

Swamp

Edited by Swampstomper Al
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Hit all links for a look see.  Some titles are misleading  .  Some of the data base list mines by name, Primary and other minerals along with composition of mineral sources.

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I should mention Clay & Co have geological bulletins on the mylandmatters site..
Came across a prelim. report titled "Gold Deposits of Georgia" dated 1896 & put together by
a state geologist and a couple assistants as a Geological Survey of Georgia bulletin..
Nice find for us eastern gold belts tinkerers I must admit..
Thanks guys & gals @ there.. :)

Swamp

Edited by Swampstomper Al
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Andyy,

 

When you find out please tell me; I am in the same area as you.  I have researched quite a bit and not found anything useful.

 

The most useful source for me finding my locations is the USGS maps, 1970's and earlier only.  I look for the Prospects indicated by X's; the shafts with an arrow and the tunnels with a square half filled diagonally with an X.

 

After a couple years of doing this once or twice a month, I have come to the conclusion that researching mining operations and their the workings in the area and finding good info to put boots on the ground on a specific site is next to impossible.  Most tunnels and diggings I have been to, even if on a map, are not documented anywhere I can find.  These are often small time ops.  An example is a tunnel I went to last month which I just happened to walk upon in a wash.  The tunnel went straight down into the ground, a hard rock operation, probably dug by two people, with one lowered on a block and tackle to remove the ore.  I was excited when I found the can for the papers, but the papers had long ago rotted away.  A search of the USGS maps found nothing, and nothing was documented on the site anywhere I could find.  I found a little copper ore outside the shaft, so I think that is what those old timers were after.

 

Another unclaimed area I went to was documented as having pulled 50 ounces of gold out of the ground.  This lead me to a series of diggings in about a mile square area.  I detected nothing but garbage.  I think it had been hit hard with a detector first.  Once I read the report further, I think it was in an old mica mine that operated when mica used to have the same value as silver does today.  If gold was recovered at all, from the site, then I'm sure it was a byproduct.

 

I've also noticed that the well documented sites tend to be either claimed or owned as a patented claim.  The best local example I can give you is the Dragon Mine.  There's a bit of info on that available on the web, but it is not available to detect.

 

Most of the diggings in the LSD area are small time which a few people working together could do, with a few medium sized ops, like the Eagle Cloud Mine.  For that mine, I didn't find much info on production, and I think it was claimed last I checked.  Maybe the Area by the GPAA claims where the dry land dredge used to operate was big time, but the only large operation I can find is the Vulture mine, but I believe that is not free mill gold.

 

I think most tunnels I come across are older diggings for things other than gold such as copper, mercury, maganese, and lead.  Things small timers can't go after for a profit.

 

Don't get me wrong.  I will never stop looking into this stuff because I do enjoy getting out to these places.

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I have used this website to download mines in arizona: https://mrdata.usgs.gov/mrds/find-mrds.php   It is good for looking up individual mines or downloading the group to google earth.  But the information section does not usually give too much information, other than the primary mineral being mined.

Swamp - most of the USGS information I find are publications on geologic maps, which are very helpful.  I haven't really found many useful publications on particular mines, so it is possible I am just not investigating the correct areas of the site. 

Then I have heard other prospectors making out brief references to using USGS on their channels (to find Free Milling Gold), without providing any links or details backing up mining information.

 

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Clay's Mylandmatters.org is definitely a useful site ...  :thumbsupanim   I use this daily.

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Try this search engine.  Covers way more data bases.  https://search.usa.gov/search/advanced?affiliate=usgs

 

I can pull up this list searching .   Each mine listed provides tons of info to include ore type. 

 

https://search.usa.gov/search?utf8=✓&affiliate=usgs&query=Arizona+Gold+Production+list+of+mines&query-quote=&query-or=&query-not=&filetype=&filter=1&commit=Advanced+Search

 

Doing similar search key Mining Districts.  https://search.usa.gov/search?utf8=✓&affiliate=usgs&query=Arizona+Gold+mine+districts+Production+list+of+mines&query-quote=&query-or=&query-not=&filetype=&filter=1&commit=Advanced+Search

 

Not going to get you every pot hole or minor prospect but will tell you what is in the area for sure.

Edited by homefire
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Good links, Homefire.  I get what you are saying.  You try to find the mine of interest, here, and any publications that might be applicable.

Now AzNBob says you can tell if it's Free Mill Gold by "how" it was mined.  Sounds like any mention of complex ore probably means it's bound with other stuff.  What else can we look for in the description of "how it was mined" to determine if it was free milling gold?

Andy

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Any I can find a history on comes out and tells you the ore type.  Associated Minerals and everything. 

 

No mention of Sulfides.  This would be Free milling ore.  We know Quartz Monzonite is a gold bearing ore.

 

Host or associatedAssociated

Rock typePlutonic Rock > Granitoid > Quartz Monzonite

Rock type qualifierporphyritic quartz-monzonite (adamellite), granodiorite, quartz-monzonite, and granite porphyry.

Rock unit nameSchultze Granite

Stratigraphic age (youngest)Paleocene

Host or associatedHost

Rock typeMetamorphic Rock > Schist

Rock type qualifiercoarse grained quartz-muscovite schist, fine grained quartz-sericite-chlorite schist, and fine grained amphibole schist.

Rock unit namePinal Schist

Rock descriptionPinal Schist

Stratigraphic age (youngest)Mesoproterozoic

Edited by homefire
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16 hours ago, chrisski said:

Andyy,

Most of the diggings in the LSD area are small time which a few people working together could do, with a few medium sized ops, like the Eagle Cloud Mine.  For that mine, I didn't find much info on production, and I think it was claimed last I checked.  Maybe the Area by the GPAA claims where the dry land dredge used to operate was big time, but the only large operation I can find is the Vulture mine, but I believe that is not free mill gold.

I think most tunnels I come across are older diggings for things other than gold such as copper, mercury, maganese, and lead.  Things small timers can't go after for a profit.

Don't get me wrong.  I will never stop looking into this stuff because I do enjoy getting out to these places.

I have also tried to do searches on the Eisenhower operation near the LSD and still have never found a location listed.  Yet I know it is fairly commonly known.  Just forgot to talk with people about it at the last outing. 

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On 4/4/2017 at 8:19 AM, Andyy said:

Good links, Homefire.  I get what you are saying.  You try to find the mine of interest, here, and any publications that might be applicable.

Now AzNBob says you can tell if it's Free Mill Gold by "how" it was mined.  Sounds like any mention of complex ore probably means it's bound with other stuff.  What else can we look for in the description of "how it was mined" to determine if it was free milling gold?

Andy

Andy you will find doing research that you are going to run across little known mines with very vague descriptions of the type of ore mined.  
Some your going to have to verify in person. I call it putting them on my hit list,and when I'm in the area I look at them in person and decide by the geology,equipment used or  
how it was dug and processed,and with little or no signs of placering below them probably not much free gold there! Did they use chemical or gravity separation? was it ball milled and or leached only?
Sometimes I just move on.some are just exploratory test holes that never amounted to anything after assays were done but you may still find them on a map.
Map symbols will also help. I.D. them on newer maps.
AzNuggetBob

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The newer topos in central AZ with the imagery built in have removed all "Dangerous" type things like mines and shafts, so I have to go with the 1970s and earlier.  They also do not distinguish between roads, jeep trails and foot paths very well.  Most, if pictured, look like a side street.

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