Madre De Dios, Peru 2008
Report on Cleangold Field Tests on the Madre de Dios River, Peru April 2008 Prepared by: David Plath, BS, MS Cleangold, LLC
Testing at the Chuparera
Following our work on the balsa we traveled upriver to the Los Amigos Research Station run by ACCA. During our trip we noted many balsas and beach operations. The largest balsa that we saw was the Russian operated “Drago Diana”. This dredge has sluice boxes wider than 20 feet and equally as long. When asked if this dredge was able to reach richer horizons of gold by going deeper I was told that all of the sediments in the river contained about the same amount of gold but that the benefit was being able to run even more ore without moving. The Madre de Dios River is not like many of the rivers dredged in the western US in that bedrock is never reached because the river is coursing over at least 100 feet of alluvial sediments, all of which contain gold but due to the wild nature of the river cannot be reached with current technology.
Typical beach operation on the Madre de Dios River. These sluiceboxes are probably too small to get the good recovery noted in the balsas and the chuparera where our testing took place. However, given the large number of operations such as these seen on our trip upriver, they are undoubtedly producing well enough.
Our purpose on this part of the trip was to work at a chuparera managed by Senor Hugo Miranda. The land operation was well suited to our testing because while it works in much the same manner as a balsa, the sluiceboxes are more easily adjusted for slope. In addition, we discovered during our work that the land operations have a larger percentage of the gold that is recovered in the minus 200 mesh size. I believe that this is because these areas flood annually and that the land acts as a large and very efficient sluicebox gathering the gold that normally will not settle in the swift moving river.
Dredging unit of the chuparera showing the engine, pump, and suction pipe. Plastic piping is used due to the remote location of the operation. The pipe rising on the right leads to the sluicebox
As in other locations where we have worked, we started our testing by collecting samples from tailings to see what gold was being lost and we worked with the concentrates from the carpet sluices to determine the best way to recover the gold that they are currently capturing using our mercury free method. We found that the increased amount of sub 200 mesh gold at the chuparera helped us to streamline the method and create a process that was easily as fast and more efficient than the mercury amalgamation currently in use.
Sluicebox of the chuparera showing a Cleangold test being installed.
Since the sluiceboxes are installed on poles it gave us a good opportunity to work in various locations of the sluicebox and with different slopes. In these initial tests it is always our practice to work with the flow and material as the miners normally do. In addition, we generally try to install our technology as simply as possible so that the miners do not have to built additional systems. In this way, we have found that there is little interruption to the operation and the miners do not risk their recovery while we are testing. The skill and knowledge of the operators is extremely important to our work as their methods are the result of thirty years of experience with some of the most difficult to capture gold that we have encountered. In this case, we feel that we were learning as much from the miners as they were from us.
Photomicrograph of gold recovered from carpet sluice tailings at the chuparera of Senor Hugo.
40X nominal magnification.
We discovered quickly that the fine gold can easily get beneath our test systems if our equipment was not sealed to the sluice bottom. Also, the Cleangold sluices operate best at a lower angle than the carpet sluices. The key to setting the slope of the box containing the Cleangold sluices is that some loose sands should remain on the Cleangold sluices when the dredge is shut down. Too little slope and the box will fill with ore, and too much and the Cleangold sluices will not work as well. As with the balsas, I think that these operations could benefit from better washing of the ore and reducing the flow to the sluiceboxes. Diverting more process water to extend the ore washing while reducing the amount of material and water that is going to the sluiceboxes by classifying to a smaller size will improve recovery of the present system and improve the conditions for using Cleangold sluices.
Photomicrograph of gold less than 200 mesh recovered from the carpets. 40X nominal magnification.
Using our more streamlined recovery procedure we are able to recover the gold from the carpet sluices and estimate the volume of gold in each size fraction. For the chuparera, the size range estimates of the gold captured by the carpet sluices were as follows:
greater than 100 mesh- 40% of the gold
less than 100 mesh but greater than 200 mesh- 45% of the gold
less than 200 mesh- 15% of the gold
Gold recovered from crushed hardrock ore from Arequipa, Peru. 40X nominal magnification.
So, fully 60% of the gold currently being recovered from the carpet sluices at the chuparera is less than 100 mesh. In comparison, the gold recovered from the balsa carpet concentrates had only 15% of the gold smaller than 100 mesh.
Recovery of Gold from Carpet Sluice Concentrates
One of our most important tasks during our testing in Madre de Dios was to determine the best method for the recovery of gold from the current operations without using mercury. In our initial testing at the balsa it was important for us to separate all of the concentrates into specific sizes so that we could learn more about the gold and about the current operations. Unfortunately this meant that it appeared that our method was slow and less impressive to the miners, even though the savings in mercury would offset the time needed to recover the gold. However, as we gained experience with the fine and thin gold of Madre de Dios we were able to streamline many of the steps and by the end of our testing we had developed a method that was as fast but more efficient than amalgamation. In addition, the losses associated with amalgamation, that we illustrated above, as well as the improved control over the gold resulted in a very spirited discussion at our last demonstration with the miners coming up with ideas on their own that demonstrated to me that they were understanding the method and making it their own.
Conclusions and Acknowledgements
The miners of Madre de Dios have shown me that their methods and understanding of fine gold recovery are equal to and in most cases better than any group that Cleangold has worked with to date. They freely share their experiences with other miners in the region through their miners association in Puerto Maldonado. This structured and scientific approach to their mining will give them the best opportunity to implement the new tools that we have shared with them. We learned about the gold of Madre de Dios as the miners did, through experimentation and observation and it is due to the fine and thin nature of the gold in this region that nature was able to provide such a laboratory. The gold from their carpet sluices can be simply and efficiently recovered from their concentrates without mercury. The Cleangold equipment to do this will cost approximately $300 USD and the savings in mercury will pay for this in a matter of weeks.
The world is demanding gold from sustainable mining and will pay a premium for this gold. The savings in human health terms that comes from not using mercury cannot be calculated. However, gold won using mercury is won at the price of learning disabilities in the children of the region, a price no parent should be willing to pay.
The Russian balsa, “Drago Diana”, in operation.
The high sediment load and constant erosion of the river banks of the Madre de Dios River when compared to the minor contribution of silt to the river from mining operations indicates that this mining could be very sustainable.
Cleangold would like to thank Kristina Shafer of Artminers for the financial support and opportunity to extend our testing into a new region, Dr. Joe Bishop and ACEER for their financial and logistical support of the project, Dr. Nigel Pitman and ACCA for their support and use of their facilities during our stay, Senor Aquilles Velasquez for allowing us to work on his balsa, Senor Hugo Miranda for allowing us to work at his chuparera, Senor Miguel Herrera and the Puerto Maldonado Miners Association for their interest, Senor Manuel Reinosa Rivas of the Peruvian Miners Association AMASUC for his very careful observation and pertinent discussions and for his association’s interest in working mercury free, and finally to our interpreter Rocio Martinez who left behind her new baby Stephano to join us in this work for the people of Peru. For Cleangold, this is just the beginning of our work in Peru. We now have samples of crushed ore from Senor Manuel’s hardrock mine in our laboratory and testing is showing us that this process too can be helped by Cleangold technology and the use of mercury may no longer be needed for this kind of mining in Peru.
