Dredging for Gold

This article was originally published on Gold Investing News on June 20, 2011.

With gold repeatedly testing record-highs, there is an increased incentive for explorers to locate new reserves of the precious metal. The heightened competition to locate deposits has explorers getting creative on where and how they conduct their search.
Typically, when you think of gold mining, an underground or open-pit hard rock mining operation comes to mind, however; historically, prospectors looked for placer gold deposits in rivers and stream-beds, and used simple techniques, such as gold panning as exploration tools.
The basic concept of retrieving gold via placer mining has not changed since the early gold rushes. Placer mining takes advantage of the fact that gold is both inert, and dense/heavy. What this means is that gold can be eroded from its original bed-rock source, and transported for miles without undergoing chemical changes. Often, down-stream from a good bedrock source there will be a significant accumulation of placer gold. Sorting placer gold from the worthless sand and gravel is easily accomplished with techniques such as panning. Because gold is dense, when a slurry containing gold, rocks, and water is swirled in a pan, the other materials wash away, leaving behind the gold. The original placer miners used gold pans, sluice boxes and rockers. For larger-scale placer mining operations, gold-dredges first appeared in the early 1900’s as massive, multistory machines capable of dredging vast amounts of sediment at the bottom of water bodies, and then sifting through this sediment to locate gold.
Since its early days, gold dredging has evolved tremendously, and now is a technique that is successfully employed by both hobbyist prospectors and large miners. Small suction machines are currently marketed as “gold dredges” to individuals interested in running a small, few person mining operations. At a commercial level, gold dredging is used around the world including in Africa, Alaska, and New Zealand.
There are a few different dredging techniques employed by the large-scale miners. One is to use suction dredgers. These suction dredgers are essentially underwater vacuum cleaners that suction up sediment and rocks from a stream bottom. The material is then run through a separation system that isolates the valuable materials i.e. gold, from the unwanted materials. Suction dredging is mostly done in a very dynamic environment, such as a natural stream or river. When dredging areas of the ocean floor for gold, a trailing suction hopper dredger is used- which is a large ocean going vessel. When the vessel starts dredging, the ship reduces its speed and then lowers the suction pipes on both sides of the ship all the way to the seabed. Sand pumps transfer the sand dredged up by the suction head into the hold or hopper. The excess water is drained of via the overflow pipes. When the hopper is full, the ship transports the material to another area, where it is sorted. When dredging through compacted materials, explorers can use another technique called cutter suction. A cutter suction dredge has a rotary cutting head, or other excavating tool that can break up compacted material. The loosened material can then be “dredged.”
It is important to note that gold-dredging, like many mining operations, conjures up some environmental concerns. Just as mining activities on land disrupt the surface, dredging operations disrupt the underwater environment. Of particular concern in terms of dredging operations is when these operations take place in fish-bearing streams. In many areas of the world, this concerns is negated by only allowing dredging operations during certain times of the year, when their will be minimal impact to fisheries.
Interest in dredging as a means to access valuable materials has increased over the past few years. Now, even diamond mining giant De Beers has formed a company branch, called De Beers Marine Group that is active in marine mining, for diamonds. In their marine branch, De Beers uses dredging in conjunction with other exploration methods. Dredging is used to remove overburden in areas with very wet ground conditions. Their dredges are also equipped with a floating treatment plant to treat low-grade diamond-bearing overburden. This method, of removing the overburden with a dredge is also commonly employed in gold mining. While the dredge is primarily used to remove overburden, it can also sift through the removed material to locate nuggets of gold that would have otherwise been missed.
Sunergy Gold (OTC:SNEY) is a Nevada-based company that is engaged in the evaluation, acquisition, exploration, planned operation and advancement to production of largely alluvial gold/silver/diamond development projects in Ghana and Sierra Leone. Sunergy owns 100 percent of the 150 sq.km. Nyinahin mining concession in Ghana, with a full prospecting license. Historically, in Ghana, more than 1.45 million ounces of gold was recovered from the Offin River. Sunergy is currently into its second month of dredging at its gold/rare earth property, the Pampana River Project in Sierra Leone.