Angus MacKirk Grubstake

Dredger Joined: 22 May 2010 Posts: 605

Angus MacKirk Grubstake

Bob G and I met up with Sam, KevNC, SCMike, and Will-D south of Morganton for a little prospecting fun last week. I finally had time to study and evaluate the Angus MacKirk line of sluices, this one was Bobg's Grubstake.

First of all, I am really pleased with the ease of set up and clean-up. It takes just a sip of water to run 12 minus. Even with repeatedly overloading, it cleared out in a reasonable time. So, for dinking around for an afternoon of prospecting, it certainly fills the bill. The Grubstake does not have the dimensions to handle much bigger material, as ½ inch material overpowered the riffles and bounced things around pretty much. I did see an increase in heavies and gold exiting the sluice in the presence of 1/2” material, so I would say start with a 3/8” or 1/4” and work your way down until you get the fewest losses.

I was actually sampling with the Grubstake at first, actually filling the top with bank run material and letting it run. Pretty interesting process with no particularly meaningful results, but it will show gold under those conditions. I actually think it could be a very useful sampling tool if you had enough of them to set some standards and to test them accordingly.

You need to test behind this sluice, as it was losing lots of -50 gold due to the competition with the 12 mesh gangue. I think the problem may have been the last riffle and boil box, as they stayed clogged, whether running bank run, or 12 mesh only, and I never found the first piece of gold in either.. The slope changes and water flow changes I made did not seem to change things all that much, which leads me to believe a little longer sluice may help. I saw from Daubster's Explorer that the Explorer has a little longer soak time since the Explorer is longer.

The Grubstake is perfectly suited for it's design parameters. Just don't expect to move 3 cubic yards per hour through it. Once something enters one of the step riffles, it will bounce around and sort as long as there is enough current to give it lift, otherwise it just sits there and keeps everything else from bouncing. Once again, you need to classify. My testing showed that the sluice was most effective and efficient when it would roll a ¼ inch rock out of the sluice. KevNC Tells me the big AU Trap will handle big gangue in fast water very well, so that will be my next attempt.

I would appreciate any technical observations you may have as well, about this fine line of equipment. I know there are many AMers on the forum, and now I see why.

Has anyone used any of these sluices with a larger than recommended slope, but lower water flow??

Sam