Some Assay Questions

Yukon99669

Jr. Member
Jul 30, 2020
68
99
Alaska and Colorado
Primary Interest:
Prospecting
I need a bit of advice on getting a cpl assays done.
I’ve been prospecting a new claim in Colorado (Gilpin County). We’re in and adjacent to a year round creek that comes from a spring that originates a ways beyond the claim. We’re near the lowest point of the stream that ultimately joins Upper Clear Creek.
Despite being quite rocky, the ground is nicely stratified and easy to read. About 3 feet down there is dense layer of red oxidized soil. Below that is a dense dark black almost clay layer that is insanely full of mica/pyrite/etc… Below that layer is a gravel layer sitting on rock (not sure if we’re on bedrock yet, but it’s a solid rock layer that actually has some deep hollow sounding sections.
We’re running a Trommel w/ 1/4” screen into a Gold Hog sluice that feeds into a flared section of vortex mat (Gold Cube Type).
We then classify cons and reduce them with a very finely tuned Gold Hog Washer Mat….finishing w/ a pan.
We’re finding almost nothing above -100 mesh. But there is a significant amount of super-fine gold in the -100 range. Actually most is -200.
My intention is to get a fire assay on my -100 cons (after the washer mat and before panning) for Au/Ag initially.
Pending promising results I would then get an XRF Analysis. I’d use the XRF to nail down a smelting flux recipe.

Am I on the right track to deal with this material?

Regarding the assay…I’m assuming that I would want to leave in magnetics? I usually pull them out ahead of the washer mat step.

Any other advice in this department?
 

Upvote 1

arizau

Bronze Member
May 2, 2014
2,479
3,854
AZ
Detector(s) used
Beach High Banker, Sweep Jig, Whippet Dry Washer, Lobo ST, 1/2 width 2 tray Gold Cube, numerous pans, rocker box, and home made fluid bed and stream sluices.
Primary Interest:
Prospecting
I need a bit of advice on getting a cpl assays done.
I’ve been prospecting a new claim in Colorado (Gilpin County). We’re in and adjacent to a year round creek that comes from a spring that originates a ways beyond the claim. We’re near the lowest point of the stream that ultimately joins Upper Clear Creek.
Despite being quite rocky, the ground is nicely stratified and easy to read. About 3 feet down there is dense layer of red oxidized soil. Below that is a dense dark black almost clay layer that is insanely full of mica/pyrite/etc… Below that layer is a gravel layer sitting on rock (not sure if we’re on bedrock yet, but it’s a solid rock layer that actually has some deep hollow sounding sections.
We’re running a Trommel w/ 1/4” screen into a Gold Hog sluice that feeds into a flared section of vortex mat (Gold Cube Type).
We then classify cons and reduce them with a very finely tuned Gold Hog Washer Mat….finishing w/ a pan.
We’re finding almost nothing above -100 mesh. But there is a significant amount of super-fine gold in the -100 range. Actually most is -200.
My intention is to get a fire assay on my -100 cons (after the washer mat and before panning) for Au/Ag initially.
Pending promising results I would then get an XRF Analysis. I’d use the XRF to nail down a smelting flux recipe.

Am I on the right track to deal with this material?

Regarding the assay…I’m assuming that I would want to leave in magnetics? I usually pull them out ahead of the washer mat step.

Any other advice in this department?
For me, too many questions in my mind. The info you provide is confusing but, I think, in a round about way, you are trying to figure out a way to separate out the almost microscopic gold in your concentrates. Am I wrong?
 

Last edited:
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Yukon99669

Jr. Member
Jul 30, 2020
68
99
Alaska and Colorado
Primary Interest:
Prospecting
Sorry if it comes across as a vague question….I’m sure I provided far too much info, I just wanted you to know more or less what I was working with and how I got here in case it made any difference.

…So Not so much “how”, unless it appears that I’m absolutely barking up the wrong tree. I’ve used a lot of recovery methods for fine Gold with mostly mediocre success, and never with material quite this worthwhile….so I want to get it right.

My question mainly is if the Assay scenario is on track?
…and do I leave in or take out magnetics ahead of either analysis Fire Assay or XRF?

Sorry again if I created any confusion!
 

arizau

Bronze Member
May 2, 2014
2,479
3,854
AZ
Detector(s) used
Beach High Banker, Sweep Jig, Whippet Dry Washer, Lobo ST, 1/2 width 2 tray Gold Cube, numerous pans, rocker box, and home made fluid bed and stream sluices.
Primary Interest:
Prospecting
Sorry if it comes across as a vague question….I’m sure I provided far too much info, I just wanted you to know more or less what I was working with and how I got here in case it made any difference.

…So Not so much “how”, unless it appears that I’m absolutely barking up the wrong tree. I’ve used a lot of recovery methods for fine Gold with mostly mediocre success, and never with material quite this worthwhile….so I want to get it right.

My question mainly is if the Assay scenario is on track?
…and do I leave in or take out magnetics ahead of either analysis Fire Assay or XRF?

Sorry again if I created any confusion!
Assays on placer concentrates are not normally done as the results represent only what is contained in that particular sample.....not any other particular whole due to the possibility of "the nugget effect". What is your reason for wanting an assay?

You mentioned +/-100 and 200 mesh sizing for most of your gold. Have you created batches of such sizing and panned them separately? If you have substantial gold in your cons then you should be able to pan some pretty clean gold by doing so.
 

Bonaro

Hero Member
Aug 9, 2004
977
2,213
Olympia WA
Detector(s) used
Minelab Xterra 70, Minelab SD 2200d, 2.5", 3", 4"and several Keene 5" production dredges, Knelson Centrifuge, Gold screw automatic panner
Primary Interest:
Prospecting
Mining is all about removing everything that is not gold. Removing magnetics are a must.
You need to evaluate if the fine gold you can recover is worth more that the labor to extract it.
 

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