Looking for Sulfides

[GoldReport]

Hello esteemed members of the board.

In my local area there are no commercial gold mines and never really have been. Through research, I came across an old State Geologist Report from the late 1800s. In it they mention that some gold was found alongside pyrite. At the time it was not of a high enough concentration that they were interested in it, but it has got me searching for this elusive deposit. I am located in the Northeast US where there is virtually no lode gold deposits to speak of. ( hardly any placer either )

I went out searching today to see if I could find this pyrite, I used a combination of the report I found with geologic maps to identify the units in question. The report describes the pyrite found at the contact of two distinct geologic units which only crop out in a few places that I have so far found. My first instinct is to locate places where streams have cut through this geologic contact and pan samples downstream of that. I would have done that today but underestimated how big of a drop I was facing and ran out of sunlight before I could find a good place in the stream where any material could build up. I was at the top of a series of short but steep water falls and only made it down about halfway before dusk started to set in.

The question I have for you all today: is there is a good way to locate sulfides/pyrite in the ground other than just visual examination?

The rock around here is quite mossy and full of lichen. I suppose I could take my wire brush and clean off any outcrops I suspect would be good but that seems inefficient and time consuming. While hiking today I saw samples on the ground with good iron staining (in a shale rock which doesn't seem quite normal to me) but seeing iron staining around here doesn't make me feel any better as there is considerable magnetite all over, I live within 5 miles of a handful of old workings.

Any tips?

I plan to keep searching but am not extremely confident for a couple reasons: around the time of this geologist report there were many scams of people finding gold so the information is unreliable at best, and if there was any decent gold to be found I think someone would have already done so given the lack of other gold deposits. I don't have a metal detector and it's not in the budget to buy one at the moment.

Will update as the hunt continues...
Thanks!

 

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[N-Lionberger]

Do you have the rest of that report? In your prospecting have you seen any conglomerates?

 

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[GoldReport]

Do you have the rest of that report? In your prospecting have you seen any conglomerates?

I'll send you a DM with the report but there isn't much more mention of the gold.

The conglomerate formation is quite extensive and easy to find. It forms the crest of a ridge about 30 or so miles long. The base of the formation where it contacts the shale is what I'm interested in but is often buried and where it crops out is often mossy.

 

[Assembler]

Yes, and was associated with pyrite. My main question, which I probably didn't word very well, is if there's any tricks to finding sulfides (pyrite) in outcrops when the outcrops tend to be mossy/vegetated. Im planning to head out tomorrow and will take my steel wire brush with me to help but any other ides are welcome.

The pyrite could be in any of the rock types within the conglomerate however the quartz's may be the best.
This is likely out of the question to use however you asked, How about a pressure washer for the moss?

For tomorrow the wire brush should work.

 

[N-Lionberger]

Pyrite doesn’t form in veins in conglomerate. Conglomerate is made from compacted river gravels and sand. The pyrite was originally deposited as part of a placer.

 

[Assembler]

One formation type you may want to look for is:

Sulfide reacts with iron: If iron is present, the sulfide reacts with the iron to form iron sulfide crystals, or pyrite.

Pyrite is found in many environments it is up to you to find or figure out the event or environment of the formation.

 

[N-Lionberger]

If I were in your shoes I would locate where the conglomerate meets bedrock and beat it up with a pick and sample with a pan.

 

[GoldReport]

If I were in your shoes I would locate where the conglomerate meets bedrock and beat it up with a pick and sample with a pan.

Thats probably what I will be doing. There are a couple of streams that cut through that contact zone which I plan to pan in addition.

 

[N-Lionberger]

Thats probably what I will be doing. There are a couple of streams that cut through that contact zone which I plan to pan in addition.

If you have a sluice box it will really speed up sampling.

 

[N-Lionberger]

We have a lot of conglomerates here in California often referred to as miners cement. Ancient riverbeds made high and dry by geological processes. Hydraulic mining was the main method of mining the cement but underground drift mining aka tunneling along on top of the bedrock was also practiced, especially in the early days before the infrastructure was in place for hydraulicking or in locations covered in rock such as under lava caps. This is an interesting subject you’ve brought up, the recovery of gold bearing ore from a placer source.

 

[Assembler]

At high temperatures (~ 500 degree C and above) sulfides can undergo partial melting, combined with fluid flow, and by this process be remobilized and later re-deposited in segregated or vein-likeforms.

The vein-like structure can also be spotted with your eyes.

If you get a chance to look at geology metamorphism reports for the area see if there is contact zones that the temperatures are more in the 300 degree C range where pyrite sulfidation growth curve can take place. The reports may refer to Pyrite-pyrrhotite sulfidation curve depending on the formation tempertures. You can spot this in the rock as well with your eyes or better yet with magnification.

At later metamorphic stages pyrite starts to form in grain-boundaries of pyrrhotite. In order for pyrite to form pyrrhotite, an oxidation reaction is required.

 

[Assembler]

Pyrrhotite is an iron sulfide mineral that is often found in marine sedimentary rocks, but can also be found in igneous and metamorphic rocks. It is a nonstoichiometric variant of the mineral troilite, with the formula Fe(1-x)S. Pyrrhotite is weakly magnetic and has a metallic luster, and is often brassy or bronze in color. It is commonly associated with other sulfide minerals, such as pyrite, pentlandite, chalcopyrite, and magnetite.

 

[Assembler]

Thats probably what I will be doing. There are a couple of streams that cut through that contact zone which I plan to pan in addition.

Do you have access to geology reports that cover the area contact zones?
What do the reports point out?