Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/853705
12 AGGREGATES MANAGER / August 2017 APPLICATIONS the mature river plaster ground, because that's where the deepest gold lies, Turin says. And finding those deep channels would be key if the crew wanted to meet Hoffman's ambitious season goal of 5,000 ounces — worth upwards of $5 million. The bottom of the claim's gold deposit consists of 3- to 4-foot boulders encased in mud, which can have gold settled within the mud, Turin says. That makes processing the rocks more chal- lenging, because the larger stones have to be scrubbed clean to remove the gold. The process starts with a wet wash grizzly feeder, which shakes the rocks down and starts cleaning the bigger boulders. The larger rocks bounce across the top of the feeder, and the smaller rocks, dirt, and gold that are washed off the boulders are transferred to a blademill. The blademill scrubs the rock with spiral flights and breaks the clay off with paddles. Material is then fed to the combo screen, which separates it based on size. Any material smaller then ½-inch-minus goes into the sluice box, where the gold is trapped in the riffles and carpet. At the end of the day, the crew cleans the sluice box and recovers the fine gold material, Turin says. It didn't take long, however, before Hoffman and Turin realized that they were not hitting the pockets of rich gold they had been hoping for. "The challenge with this site is that the dredge went up the middle of this valley," Turin says. "So we wanted to do two things: get underneath where the dredge went, and get the side pay that it left. "What we found was that the dredge did a great job. We were chasing a pay zone where we thought we would be able to run about 12 hours a day. In the end, we didn't find the pockets of rich gold that exist in the claim." Smooth screening Although Turin had plenty of experience with a variety of screens in his mining career, he gives the combo screen high marks. "I love the combo screen," he says. "I was a bit apprehensive initially, with the added size and height and the fact that it looked to me like it was go- ing to be out of balance, but boy, once we fired it up, it ran so smoothly." "Since we turned it on, it's the smoothest-running screen we've ever used," Hoffman adds. The combo screen from Johnson Crushers International is a new breed of screen that combines characteristics of incline and horizontal screens, and delivers productivity, efficiency, and flexibility in wet and dry applications, according to Nick Hahn, product de- velopment manager for JCI. The combo screen also offers a sloped feed zone for quicker fines separation and provides the benefits of a triple-shaft vibrating mechanism. These advantages include anti-plugging/blinding, extended bear- ing life, application flexibility, and stroke amplitude adjustment, Hahn says. "The combo screen allows you to quickly get your oversized material out first, and then at the bottom you're getting perfect fine screening," Turin says. "At the beginning, the material's not just moving with the vibration, but it's rolling over itself, which then allows it to get into the opening." Turin is no stranger to equipment from JCI. Long before joining Gold Rush, he earned his degree as a civil engineer and served as vice president and quarry manager of his family's aggregate business, Mt. Hood Rock, just a couple of hours away from the Eugene, Ore.-based manufacturing facility. "We've used JCI products for years," Turin says. "Their equipment has always held up for us, and it's always compet- itively priced. In my family business, we've always looked at long-term goals. We don't do things on a short-term basis — we want to know how long something is going to last. "The thing I especially like about JCI is that they're not just sitting there The deposit being mined this season — having previously been dredged — allowed the crew to sluice only 7,000 yards over the course of the season.