Northern Vertex Mining Corp. is pleased to provide the metallurgical results obtained from heap leach cyanidation (column leach) testwork on a mineralized material low grade bulk sample from the Moss Mine Gold-Silver project located in Mohave County, Arizona, USA with highlights as follows:
- Lower grade mineralized material was readily amenable to agglomeration - heap leach cyanidation treatment at the 95% -1/4" crush size with respect to Au recovery
- Gold recovery rate was more rapid for the lower grade mineralized material vs. the higher grade mineralized material (previously reported in the Amended Preliminary Economic Assessment dated June 18, 2013)
- The column leach test recoveries were 82.7% for Au and 36% for Ag
- Lower NaCN consumption was observed for the low grade mineralized material vs. high grade mineralized material
- A relatively low cement addition (4 lb/ton ore) was required for agglomeration pretreatment of the low grade mineralized material
McClelland Laboratories, Inc., Sparks, Nevada, specialists in heap leach processing, have completed metallurgical test work on the low grade mineralized material from the Moss Mine Gold-Silver Project. The primary focus was to determine if there was a relationship between grade and recovery for the higher grade mineralized material and the lower grade mineralized material.
Metallurgical lab test results indicate that lower grade mineralized material was readily amenable to agglomeration - heap leach cyanidation treatment at the 95% -1/4" crush size with respect to Au recovery. The sample tested was a bulk sample of mineralized rock, characteristic of the lower grade material that is expected during Pilot Plant Operations. The sample was prepared using a jaw/cone crusher circuit to 95%-3/4". The crushed material was then passed twice through a modified rolls crusher located in Phoenix, Arizona.
The low grade material can be leached for shorter leach times compared to the high grade material, as indicated in the Amended Preliminary Economic Assessment dated June 18, 2013. Column test gold recoveries at a 73 day leach time on the low grade material, processed 2 x thru rolls, 95%-¼" inch were 82.7% for gold and 36% for silver whereas recoveries at a 112 day leach time on the high grade material, processed 2 x thru rolls, 95%-¼ inch were 84.6% for gold and 76.6% for silver.
NaCN consumption was lower for the low grade mineralized material vs. the high grade mineralized material. As well, a relatively low quantity of cement (4 lb/ton ore) was added during agglomeration pre-treatment. Leached agglomerates were not significantly degraded during leaching and remained strong and stable. Geotechnical characterization ("load/permeability" type testing) will be required to confirm permeability of the agglomerates under planned commercial heap stack heights.