Feedback on Sampling for Dredging Please?

[starsplitter]

Newbie here. Posted this in another section but recieved very little feedback. Hoping to improve it here. I am hoping for opinions as to the viability of dredging.

We just came back from a river located at about 3,500 feet in southern Ecuador. Relatively wide. Average depth probably about 1-3 meters. We sampled with a pick, shovel, bucket, classifier, and pans.

The sampling was along the bank, in some bedrock crevices (ledges at flood level), and in the water along the shallows in likely areas. We sampled four locations along about 200 meters of river. All on the same side.

We filled 8 buckets two thirds full with classified material, we got a little less than a gram and numerous small rubies (the black sand shimmered in red). Also, the pans often turned up a faint "glow" along the edge of the black sand. Earlier, in the same area, was found a gram plus sized nugget up on the shelf.

Please give opinions as to worthiness of the sampling and what it indicates. We are considering using a dredge. Has anyone heard of a Vera dredge? Thank you.

 

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[Alaskan Adventurer]

Wow, Star. Sounds like the area has the major potential. Close to a gram in less than 8 buckets is quite rich. Nice find on the nugget. Did you try out your detector in the area?

Yes, a dredge would be very viable there. Is the area remote, or is it easy access?

You should tighten up your sampling. I generally sample in a grid formation, first followling the river. Make sure you read the river a bit and look for inside bends. Huge boulders in an inside bend has huge potential for a decent paystreak.

When you sample, take the exact same amount of gravel in each spot. I will start by digging holes following the river with about 5 meters between each hole.

Here is an example.

Hole 1- say I find 1/10th of a gram. I move forward another 5 meters.

Hole 2- Hmm, 1/8th of a gram here using the same amount of gravel and trying to match the same depth. Getting better, so I move forward 5 meters to hole #3.

Hole 3- Back to less than hold number 1, about 1/13th of a gram if weighed.. This is the point where I move back to hole 2, and sample in a grid around this hole to pinpoint the paystreak. I would be writing this all down on paper, by the way. Once you have figured out the directions of the paystreak, I will go the richest location and enlarge my hole and digging to at least a couple feet. This is where you hope that the gold is getting richer as you go deeper. Usually that is the case. You have now figured out where the richest point of the paystreak is and you can now start dredging or just digging if you decide on holding off on the dredge.

-You should at least get a good sluice, or maybe even a highbanker to speed things up.
-Classifying your cons down in the end will drastically increase the speed of your sampling, due to all the concentrates being of the same size or smaller. No larger rocks to knock your gold out of place while panning etc.

I am not the best at explaining things, but I hope you get the basic idea. Sampling in a consistant grid in a gold bearing area will increase the chance of finding some rich paystreaks. Hope this info helps. John might have a better system for you as well.

 

[Alaskan Adventurer]

Keep in mind, about 42 buckets of your average gravel will be close to a metric ton. Filling these buckets with gravel and running it through a sluice(or a highbanker) will give you an idea on how feasible the area might be for dredging. Anything over a gram per ton is actually not bad in my personal opinion. You got almost a gram with those 8 buckets, so that would be about 4-5 grams per ton, which is very rich. Most likely the deeper you go, the richer it will be as well. Looks like great potential, but you should definitely do some more testing just in case.

You will want to take multiple tests in the area when considering whether or not a dredging operation is worth the time. If the area is difficult to access, then packing fuel in will be a real pain. It comes with the territory though. This is Ecuador!

 

[starsplitter]

Alaska... thank you for the input. I made an error with the amount. It would be closer to a half a gram. Same river, with two sets of sampling for a total of about 8 buckets. In any case, your feedback is very helpful. The idea was to get a feel for the concessions and sample. All things considered, the sampling method was poor. We did not plan well enough. The entire river seems to have at least good potential. Again, thanks.

 

[Alaskan Adventurer]

Np, glad my info was useful. Even half a gram in 8 buckets is a nice find. If the area isn't too rocky, you can figure 5-7 metric tons of material a day using a 6" dredge. More experienced dredgers could probably move quite a bit more than that. Is the water clear in your river?

Let's do a little math. Half a gram in 8 buckets, so a ton of material would be about 2.5 grams. So with that amount of ground moved, you would probably bring in 10-15 grams of gold a day. Not too shabby for Ecuador. You will get about 85-90% of spot if you sell in Ecuador. Figure about $55.00 a gram, so $550.00-$825.00 a day.

This just a guess based on your first test. You could have gotten lucky and sampled in a paystreak, or this could be low for the area. It is most likely pretty low since you started your sampling in a straight section of the river. Don't forget to sample inside bends and high benches. High benches can contain very rich gold and are often overlooked.

Dave McCrackin's site, goldgold.com has some great information about proper sampling and how to optimize your dredging.

 

[starsplitter]

Thank you. Let's stay in touch.