Giant GOLD DREDGES make a comeback, Mongolian Dredge Fleet disproves drills Options

[Steppegold]

Hi Folks - I'm a newbie here, usually on Alaska Gold Forum but lived in Mongolia since 1995. Then there was just one working dredge in Mongolia, and only a few dry mines. I've been documenting the placer gold rush since, now with 135 placer mining companies working 200 placer mines, and the Mongolian Dredge Fleet now has SIX large bucket line gold dredges and about 20 smaller bucket line dredges. I'm posting to share knowhow and ideas. And I am hoping someone will volunteer pics of the Snowstorm Dredge (especially its riffles) for me to include in the Tech Manual I've nearly completed for publication.

First I'll try and post some pics of the gold dredges to see if you folks are interested. If you want to visit them it can be arranged!

We'll see how it goes - I would like to discuss PLACER DRILLING later on, as there is a systemic error that means understimation of gold reserves beneath wet floodplains. This error seems to be ignored in the USA and Canada, but please realise that the 6 giant Gold Dredges in Mongolia exist ONLY because the systemic error was corrected by the soviets just before the command economy collapsed.

Enjoy the pics and realise that - if I'm right - then large gold dredges would be profitable in USA and Canada on placers formerly written off as subeconomic grades.

cheers - Steppe

[Steppegold]

Coalbunny - you asked a good question:
"I'm more interested in the efficency of a bucketline compared to that of a suction dredge."

Its actually a bit convoluted to give a proper answer.

A BIG bucket-line dredge should recover ALL the material provided it is small enough to fit in the bucket. My friends caught a Mammoth in one of the buckets of their bucket-line dredge.

A bucket-line dredge usually swings as it cuts, and therefore it is usual to have an onboard washplant. That's OK, but the nature of the swing and dredging limits the length of the dredge, so often the space for the onboard washplant is limited. That means a brilliant dredge is likely to have a not-as-good-as-it-should-be onboard washplant, and retrofitting a new washplant is impossible without stopping production for months.

Right, now for suction dredges.

An advantage of a BIG suction dredge is that it generates slurry that can be pumped to a floating washplant sat on a barge/pontoon nearby or even at a distance. Therefore there is no limit to the size or layout of the washplant, it can be altered easily, and retrofitting can be done without any serious delay.

The disadvantage of a suction dredge is that if the material is cobbly, as it often is, then the cobbles cannot be pumped up and so one by one accumulate on the bed of the dredge pond. That is not a good idea for eventually it means that the suction dredge cannot get at the virgin material below, or if it does then the gold is liable to be dropped in the crevices between the cobbles - the dredge pond may end up carpeted in gold! In contrast a heavyweight bucket line dredge is able to rip loose bedrock.

That said, cutter suction dredges are cheaper to buy than bucket line dredges, are much more readily available as they are civil engineering dredges for rivers and coastline, and are much easier and quicker to transport, assemble, disassemble and truck to the next location. It can be as quick as a few days, but for a bucket line dredge it is usually some months, often many months.

Cutter suction dredges are probably cheaper to operate and cheap enough to also remove the overburden. Indeed a winning combination in terms of cost, speed, recovery, freedom of movement and rehabilitation is a cutter suction dredge up front to pump away the overburden followed by a bucket-line dredge that mines (and washes) only the placer.

I hope this helps a bit

Steppe