Road Machinery’s support is key in selecting equipment
About 100 miles north of the greater Los Angeles metro area is a region that once flourished with gold and silver mines. For the last half century however, mining activity has been relatively non-existent. Even though production has shut down, there are still plenty of valuable resources available in the hills that comprise the region. Golden Queen Mining Company is now going after these resources at a mine known as the Soledad Mountain Project, just south of Mojave, California.
“Once we got through the permitting process and financing was in place, we began to put in the infrastructure, including a maintenance shop and testing lab, and ordered equipment,” explained Ken Mann, Senior Manager of General Support and Administration. “Preproduction mining, which is overburden removal to reach the ore veins, began last year with a goal of getting to and harvesting the gold and silver veins by last fall. We met that goal.”
The gold and silver is located in several veins and zones that are between five and 150-feet thick, 325- to 3,000-feet long and 300- to 1,000-feet deep. Production is expected to average approximately 74,000 ounces of gold and nearly 800,000 ounces of silver per year, once full production is achieved. Projections indicate nearly 807,000 ounces of gold and 8.3 million ounces of silver production – depending on several factors – in a span of 11 years, which is the calculated life of the mine, according to a 2015 feasibility study.
“As we drill and blast in new areas, we take samples to our lab for analysis,” reported Mine Manager Tim Mazanek. “The lab determines if an area has ore or waste, and that tells us where to haul the material. Ore goes to our primary crusher, and the waste is sent to other locations in the mine for various uses.”
The primary crusher is part of a three-stage process that includes a high-pressure grinding roll (HPGR) in the third step, which sizes and prepares ore particles for heap leaching. Assessments done by Golden Queen and others showed HPGR benefits could include higher gold and silver recovery and faster extraction rates, among many others.
Producing doré bars
Golden Queen uses open-pit mining methods as well as cyanide-heap leaching and Merrill-Crowe processes to recover gold and silver from crushed ore. Construction of a massive, sloped heap-leach system was part of the infrastructure work. It consists of a clay liner, a plastic liner on top of the clay and a thick layer of rock. Mined materials are placed on top of the system and a diluted cyanide solution is sprinkled over it, dissolving the gold and silver as it goes through the rock. The resulting solution runs downhill on the plastic liner and is collected at the bottom.
Upon collection, the resulting solution goes through the Merrill-Crowe process where zinc is added because gold and silver attach to it. Those minerals are filtered off and melted down into a sludge for making doré bars – a combination of gold and silver – that are shipped to a refinery.
“At full production we’ll have four major pits and two or three smaller ones,” said Mann. “Our workforce will ultimately be about 185 people, and we’ve worked hard to hire from the local area as much as possible. Our process group that handles the cyanide solution currently operates around-the-clock. The mining group works 24 hours a day, five days a week, but eventually it will be 24/7 as well.”
Road Machinery helps build large Komatsu fleet
Golden Queen Mining uses several pieces of Komatsu equipment to mine, process and move materials. The company worked with Road Machinery, LLC to acquire HM400s that were converted into 8,000-gallon water trucks; PC240LC-11 and PC800LC-8 excavators; D275, D375 and D65 tracked dozers; a WD600 wheeled dozer; WA800 and WA900-3 wheel loaders; a GD655 motor grader; as well as HM400 articulated and 100-ton HD785-7 rigid-frame trucks.
Excavators hammer, dig and load materials while wheel loaders help fill trucks for transport to crushers. Dozers pioneer new roads, push and stockpile earth and rip in hard areas. Haul-road maintenance is accomplished with the motor grader.
“Road Machinery put together an attractive package, and Komatsu is well-known in the mining industry for its quality and reliability,” Mazanek noted. “We’re very pleased with the performance and production the Komatsu machines provide. The articulated trucks work very well for mining in small areas, and if we have additional open space, we turn to the larger HD785s for hauling massive amounts of material more efficiently.”
Road Machinery assembled the machines on-site and provided initial service work before Golden Queen mechanics took over their care. Road Machinery also opened a new facility in Mojave so that service technicians and parts are closer to the mine, as well as for supporting other customers in the area.
“That says a lot about Road Machinery’s commitment to customer service,” Mazanek remarked. “Its location is just a few miles away, and that enables us to keep less inventory on-site. It also means that they are close if we need service, but with the new Komatsu equipment, that hasn’t been an issue.”
“One of the most important aspects of choosing equipment is dealer support,” Mann added. “Road Machinery has been excellent to work with from the start. They answered all of our questions and ensured that we had the proper machines to maximize our productivity. We’ve built a great ongoing relationship with Road, especially with Steve Morico (Regional General Manager Southern California), Jack Hiatt (Project Manager) and Leonard Swett (Parts Supervisor).”
In addition to its gold and silver mining activities, Golden Queen is also focusing on aggregate products and eventually sales of these items. Waste rock and sand from overburden removal and mining activities are processed into new aggregate products, such as riprap, stone and sand. Currently, Golden Queen stockpiles these materials on-site.
Research of the mine site indicated that up to one million tons of aggregate material could be produced and made available. This production is expected to help supply the areas in relatively close proximity to the mine that are considerably short of these products. The California Department of Transportation predicts that aggregate demand in towns and counties immediately surrounding Mojave is nearly 13-million tons per year, and only about 27 percent of that need is currently being fulfilled.
“It’s a great use of the by-product from the mining process,” said Mazanek. “Eventually, we plan to sell to outside customers. We have permits in place, and we believe there is a great potential opportunity for an aggregate producer to partner with us or subcontract on-site.”