Bucket Line Dredge Efficiency

[easy goer]

Is anyone aware of a study done on the tailings from bucket line dredges? By this I mean is there any scientific data that tells what percentage of gold the dredges captured as to the amount left in the tailings? I realize there is no standard and would vary as to the size of the gold in the area prospected. I am referring to the turn of the century, 1900 to 1930's type bucket line dredge. There had been conversation on another thread about small gold, -100 mesh, while I wouldn't imagine you could make a living under the -100 mesh in most places did the bucket line dredges leave this behind in most places? What about +100 to -50? A little bigger, did they miss this? Again I realize this will vary from region to region.
You always hear that the dredges kicked out nuggets bigger than 3/4", there are billions more pieces of -50 mesh and smaller than 3/4" nuggets but there needs to be more!!

Any information would be greatly appreciated.

Easy goer

[Joe S (AK)]

I used to know an old timer in Anchorage (54 years ago) who had worked on at least one Alaskan bucket line dredge in his youth (shortly after 1910). According to him the operator at the controls was one major factor as to efficiency. There are so many variables leading to specific actions of the individuals that there would be a substantial fluctuation in the recovered (or lost) Gold amounts and sizes.

For example "Oscar the Operator" starts out first shift and is ever so conscientious. Carefully and skillfully he recovered 90% of all the available Gold, of all sizes, that went through the operation on his shift. Very little was lost.

He ended his shift and turned everything over to "Second Shift, Slap-Dash-Sam" who was slowly recovering from a world class hangover as well as a little food poisoning. 75% recovery at best. 'nuff said, I think.

Then also, the dredge would wander upstream and go through different zones containing various sizes and quantities of Gold. A fine Gold area early in the day, big chunks just after noon and completely out of the Gold in the late afternoon. Maybe the same tomorrow and maybe not. The amount of "lost Gold" could vary a lot since the concentrations of Gold in the material varied so much. Adding to that is the fact that 'lost Gold' is lost - and so no one actually knew what the real recovery should actually be.

***
Generally the Gold lost to tailings had a lot to do with the time of year, as well. Mid-summer work activity can be much less hectic than right before freeze-up. Some operations worked fast and loose and just tried to jam as much into the front of the equipment as they could - reasoning that the window of opportunity was narrow in Alaska' climate and next year they would be far away doing the same work, as quickly as possible. Many operations didn't concern themselves over the small sized powder Gold - leaving it all in the tailings for you.

[easy goer]

Joe

Thanks for the info. I have read quite a bit about dredge operations. I am hoping they ran into a bunch of boulders, outcroppings and maybe some prehistoric trees that caused them to skip significant areas that still contain gold.
I am curious if anyone has analyzed any tailings piles to see what remained. It is like history if you don't learn from it you are doomed to repeat it. I know at the end of the day that no matter what the case may be somewhere else it only matters what happens at the end of your suction nozzle.
This is just more of its winter and lets talk about mining! Sunny and 80 today, still growing cherry tomatoes and cayenne peppers with no end in sight.

Easy goer

[chickenminer]

I think Joe pretty well covered it. There is a lot of variables involved in bucket-line dredge recovery. One key factor was the Dredge master !

If you are interested in dredge history in Alaska, you should try and get a copy of the book "The Northern Gold Fleet" by Clark Spence. Out of print but a library may have a copy.
It is THE best book on dredges/history that I have read.

[easy goer]

Dick,

I think I may have found a copy at a nearby library, I will call in the morning. All else fails Amazon has it for $225 !!

Easy goer

[Geowizard]

"Sticking your neck out";

I have been mining tailings for ten years. It requires "sticking my neck out".

I didn't "go to the library". The answer to the question of what was left in the tailings is found in the tailings.

To find out how much GOLD was LOST on bedrock, in the cracks, behind the boulders and under the assorted possibilities of debris that is at or on bedrock can only be found "at or on bedrock".

Success in prospecting tailing piles relies on someone else having failed. The probability of failure in past mining is LOW. The reason is because those early miners had to stick their necks out and invest personal time and money along with a lot of hard work to travel to places like the Kougarok River in Alaska and THEN go to WORK looking for GOLD where NOBODY on earth ever looked before! Their chances of success were based on using every faculty they had to find EVERY nugget and very grain of GOLD they possibly could.

There aren't many forms of human effort in the face of all odds combined with human suffering as mining in a remote stretch of the Arctic like the Kougarok River. It gives a whole new meaning to the phrase "Sticking your neck out".

Guess what you will have to do to find the answer?

- Geowizard

[easy goer]

Geo

Thanks for the reply!
"the only thing you have to absolutely know, is the location of the library"
Albert Einstein

With all due respect I will stick with Albert on this one. I notice you enjoy the use of idioms so here's a few I enjoy "look before you leap", "haste makes waste", "leave no stone unturned", "a fool treads where wise men fear to go" and "those who cannot remember the past are condemned to repeat it".

I conceded the point that no two areas are the same and the only way I would know in my particular area is to look for myself.

My question is not as to the effort of those before me but more to the limits of their equipment. It doesn't matter how hard you work if you don't have the proper equipment. I may be asking a question that hasn't been answered yet. Has anyone ever gone behind one of these dredges and done a statistical analysis of what size gold was left and how much. May never have been done. I will continue to ask questions and follow any leads anyone is kind enough to provide.

Last idiom, my late father was fond of " an empty drum makes the loudest noise".

Easy goer

[Geowizard]

Easy,

Excellent, please report back in TEN years with YOUR results!

- Geowizard

[Joe S (AK)]

easy goer,

It seems that you might well be right on target towards learning your ground. Some of the losses, certainly variable, do come from the limitations of the old timer's equipment, some due to the sense of urgency over a short mining window and some on earlier mining techniques, procedures and good 'ole experience (or lack of it). All of those (and probably others, too, combine to end up with the loss rate for your specific ground.

It seems to me that the various causes for loss (and the richness of the ground) all combine to give your ground a unique % of loss - something that you will quickly pick up on by analyzing your actual recoveries. For example, a bucket line dredge operator was known to be cautious in not digging the pay fully down on or into the fractured bedrock. Experienced operators would not foolishly dig deeply into those areas in the openings in the bedrock because breakage of the bucket line could result. As a result of that danger to productivity a smart operator would adjust the depth of dig to 'feel' the bedrock with the buckets and adjust the depth of the dig to gently scrape the tops of the bedrock. If the untouched material is somehow exposed today then you're into 'virgin ground' and life is good.

Another fact is that the "stuff" on top of the tailing pile came from the deepest layers. I have found that, dependent upon previous recovery rates, the top foot or two of tailing piles can sometimes be surprisingly productive.

In addition, occasionally in tailing piles I've found large clay balls that had survived the travel through the dredge's sluice and then been deposited in the tailings. Clay, which was hard and 'troublesome' when freshly dug will weather down and disintegrate over time. Find an old clay ball (some were large) in the tailings and give it a look.

After all is said and done you, poking and panning in your tailing piles, will be the one who comes up as "the expert".

I had mentioned the old timer I spent hours with back in the 60s. One story he told me bears repeating.

One summer 'the crew' was grinding their way up a so-so rich stream. Up and up they went until they came upon a bedrock dike. The crew chief sent some of the guys over the dike to test the other side - the thought being that they weren't going OVER that dike and so they were about to work their way back downstream.

The
Test Pan Crew came back and the results changed the rest of their summer. The ground was so rich (the dike was a solid 'riffle' to the Gold flow) that the entire crew - everyone- grabbed a pan and the available shovels and hand panned the area 15 to 20 feet above the dike. It took the rest of the summer - but the almost abandoned ground was SOOooooo rich that the entire crew "made out well".

Afterwards the dredge was turned and began chewing it's way back downstream. No - he never told me the name of the stream (if, in fact, it even had one).

All the best of fortune to you this coming spring.

Joe

[Geowizard]

Down under;

Yup, the test pan crew tested bedrock 30 feet down under.

- Geowizard