Leaching of Kvanefjeld concentrate

Greenland Minerals and Energy owns the Kvanefjeld uranium and rare earth element project in southern Greenland. The project has completed a Pre-Feasibility study which shows an economically viable project to produce substantial quantities of uranium oxide and rare earth oxide intermediate products. This Pre-Feasibility study was released in April 2012 with Feasibility activities already initiated to take the project through to commercialisation. Testwork has shown that silica dissolution and re-precipitation can be controlled during the leaching of Kvanefjeld concentrate. Extended residence times and high temperature are important for silica control. In addition, the rate of acid addition must be slow enough to allow silica to precipitate faster than it leaches. High acid addition is needed to produce high extractions of values with atmospheric leaching. Monazite is noted as being a refractory mineral in the process, which reduces light rare earth extraction. Acid baking is highly effective for extraction of light rare earth elements. High temperature of 290°C is needed to breakdown the monazite mineral in addition to steenstrupine. Heavy rare earth and uranium extractions were observed to be lower than atmospheric leaching. This could be improved with further testwork focusing on increasing the acid dose or retaining more acid in acid bake process. High acid conditions are known to leach the alkaline mineral steenstrupine effectively however acid baking is needed to extract values from monazite. However mineralogical investigations suggest that monazite may not be an important host of light rare earth elements across the entire deposit. Some ore types produced very high recoveries of light rare earths with atmospheric leaching with only modest decreases in heavy rare earth recoveries. The main concentrate sample tested produced the lowest light rare earth extractions and therefore also has the highest monazite content. The atmospheric leaching test appears to act as an accurate proxy for the identification of monazite across the orebody.