historic dredge operation question

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historic dredge operation question

Postby JasonG » Mon Jun 14, 2010 7:28 pm

Was mercury used on any of the old dredging operations? Especially wondering about the operations in SW Oregon, but curious about all of them.

Reason I'm asking is I'm looking at buying some land that is mostly old dredge tailings and I can't find any historical information about the operation. I am planning on building a stone house out of the larger cobbles in the tailings (after properly processing the tailings for gold first :) ) and I really would prefer not to have mercury in my walls.

There was no mill nearby, which in my experience has been where most the mercury I find has come from, but I'm wondering if they also used it in their dredge sluices?
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Re: historic dredge operation question

Postby Hoser John » Tue Jun 15, 2010 6:36 am

Always,go online to your state geo /mines minerals/ office and publications available at (they were) as we utilized them in the mid 80's on a project outta Bend-John
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Re: historic dredge operation question

Postby Bonaro » Tue Jun 15, 2010 10:26 am

1st. are you talking about dredge tailing piles or hand stacked cobble piles left by the Chinese? If Chinese then probably no HG. The two can be hard to tell apart.

Using HG flotation tables inside large bucketline dredges was common practice because it worked very well. The attached pics show the actual HG tables inside one of these dredges. It's really quite amazing. Huge cascading arrays of steel chutes filled with wooden planks which had pockets or channels cut into them were poured full of HG (many gallons). The dredge would scoop the river bottom and run everything through a large trommel or grizzley to reject the oversize. This oversize was run out the back on a conveyor and stacked into piles (house building material) The classified slurry would then be run across sluices to take out the coarse gold and the fines were sent to the tables. The waste from this was run out a separate conveyor. The HG tables would be cleaned up by diverting the slurry off of one table at a time so production would never stop. Yes, a lot of HG was lost.

Now, before you freak out at the potential of a new home becoming a superfund cleanup site...go get some real and unbiased info about mercury. It is not the evil killer of children second only to plutonium that the greenwashed hoard would like you to believe. The toxicity of HG is close to that of Lead and it is a NATURALLY OCCURING element. I would be surprised if any of it found its way to the cobble piles because it would have been lost during the processing of the fines and rejected separately. Bucketline process do vary but even if HG were deposited in the cobbles, it has been subjected to weather and erosion for a century and the liquid metal has long since settled to the bottom of the valley and now rests on bedrock. Even if it were to somehow cling to the cobbles, in the manner you will be using them, you will get a much higher HG exposure by eating a can of tuna.

My advice...build your dreamhouse and please post a pic when you're done, it sounds like an awesome idea!

IMG_0660 (Large).JPG
Wooden plank with mercury pockets
IMG_0660 (Large).JPG (100.81 KiB) Viewed 3756 times

IMG_0658 (Large).JPG
This is only one side of the amalgamation table. If you look to the left you can see where another table slants off to the other side of the dredge.
IMG_0658 (Large).JPG (112.63 KiB) Viewed 3756 times

IMG_0656 (Large).JPG
The amalgamation table extends behind the bulkhead from the guy. Total dimension of tables in this dredge is probably 30'x80'
IMG_0656 (Large).JPG (118.6 KiB) Viewed 3756 times
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Re: historic dredge operation question

Postby golden optimist » Tue Jun 15, 2010 1:19 pm

Neat pictures!

Thats one of the things I really like about the new software. You can interleave text and pictures and even label the pictures.

It was worth the wait and all of the slow crap now that it is running correctly.
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Re: historic dredge operation question

Postby JasonG » Tue Jun 15, 2010 7:59 pm

Thanks Bonaro. Sounds like if I stick to piles of just larger cobbles then it'd be fine building material since it was screened off. Ill post some pics but I'm still in the land buying process and 1000 mi away so give me a few years. :D
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Re: historic dredge operation question

Postby Bonaro » Tue Jun 15, 2010 8:19 pm

You can use the fines for concrete base, just add portland. I really would not worry about HG anywhere, it has long since settled to the lowest possible point in your geology.

If you are in an area known for large gold or gold in quartz matrix, you should keep a watchful eye on those tailing piles. The bucket lines would commonly reject anything 1.5 inches and larger even if it were solid gold.
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