This placer mine worked best as a two-man operation. In addition to a truck and loader, the brothers also used an excavator to dig out, de-rock and load the raw materials into the truck. One person usually operated both the excavator and truck hauling the sediment left on the hillside by the retreating glaciers and kept the other busy with the loader feeding the paydirt into the plant.
This mine is sometimes operated by a single person, but it does require a bit of planning and organization. You have to spend one day at the source, digging, derocking and hauling material to the staging area. Then you' move to the staging area to process all of the gravel you had just hauled by feeding it through the gold plant.
Most of the time, that's the way Holloway Bar works - a one-person operation. But it's always best to have at least another person involved - you can process twice as much gravel. Some would say that would get you twice as much gold!
The truck dumped this load and went back to get another batch of material ready. I was curious to learn about the way this gold machine worked, so we walked over to the plant for a quick lesson
There are several different types of machines used in placer mining. We use a trommel/sluicebox system at Holloway Bar to extract the gold from the gravel - but this mine uses a placer mining jig instead. The one thing almost all gold mining methods have in common is their use of gravity to pull the heavy gold from the lighter materials. Jigging also uses gravity, and is one of the oldest processes used to separate heavy minerals from the lighter materials that carry them, dating back to the ancient Egyption times where it was used to separate wheat from chaff.
A jig contains a series of plungers and diaphrams that work with water and gravity to force the heavier gold to drop to the bottom and allow the lighter materials to be washed off the top, and users of these systems are quick to point out the benefits of using a jig recovery system.
Most of the advantages are in the operational end of things. For example, there's no need to shut down the operation to do cleanup - the jig is self-cleaning and produces a continuous concentrate. They also use less water than a sluicebox system - this operation is fed entirely by a gravity-fed water system, so there are no pump operating costs to contend with. There are also relatiely few moving parts, so jigging systems tend to be quite reliable and while not maintenance free, the upkeep is generally a little easier. Jigs can also be used for a variety of minerals, as long as the metals are heavier than the surrounding soil.
Jigs were used extensively in coal and base metal recovery at the turn of century, but were't used in placer mining until 1914 and became very popular with placer miners until 1942 when gold production came to a standstill. Gold mining has since recovered, but jigging hasn't seen the resurgence some predicted.
