Friday, July 15, 2011

Dawson City, Yukon - 4 - Dredge #4

Saturday, July 9

We learned a lot today about placer gold and placer mining. During our various trips to Colorado we'd seen the kinds of mines where the gold was in veins in hard rock. The miners would blast it out, and the ore needed to be stamped, or crushed, to get the gold separated from its surrounding rock. Placer gold, on the other hand, is already separate from the rock, and is usually in the form of small sand grain-sized pieces or small nuggets. It's located in the stream gravels, especially in Bonanza and Hunker Creeks south of Dawson City.

The most expedient way to get this gold out of the stream gravels was to use a dredge. Much like dredges that clear mud and silt out of a harbor, gold dredges pick up the rocky stream gravel, put it through a giant hopper and then wash it through sluices. The gold dust, being heavier than the gravel and the water filtered down to the mats in the sluices and then was washed out by hand by the miners.

We drove about 8 miles up Bonanza Creek to the site of Dreedge #4. It has been maintained by Parks Canada as a historical site, and they give tours through it several times a day.

The white tent covers the workmen who are rebuilding the hull.

This diagram shows the process. The dredge sits on a giant pond of water, which it takes with it as it moves around the canyon. The dredge scoops up the gravel using a system of 64 large iron buckets, the gravel goes through the hopper in the middle of the dredge, and the excess gravel goes out the back of the machine, filling up the pond in the rear as the front of the machine creates the pond. The dredge is indeed a boat--sitting on a body of water up to 54 feet deep.

Our guide for the tour was the same man who portrayed Father Judge yesterday at the Palace Grand Theater.

These are a couple of the buckets used to scoop up the gravel.

The view out the side of the dredge.

The hopper, which let only small pieces of rock (and hopefully gold) through. The larger chunks of rock continued down through the hopper and were expelled out the back.

These are the sluices. The small pieces of sand and gravel were carried here by water--lots of water--and a system of netting and mats trapped the heavier gold dust. Periodically the machine would stop and the operators would rinse out the mats, hoping to find gold dust which would be melted and formed into bars.

This was the room from which a man operated the front of the dredge. All he did was move the front boom back and forth as the dredge moved forward. The radiator in the middle was to keep the hydraulic levers warm enough to operate.

This little bird was grooming itself on a cable outside the window.

This dredge was originally built on the Klondike River, about 12 miles from where it sits now. It made its way upstream over a period of about 18 years, and eventually stopped where it sits.

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