Velocity Minerals Ltd. (TSXV:VLC) (“Velocity” or the “Company”) announces that it has received positive results from comminution, flotation & gravity recovery, and leach test work on a bulk sample representative of the entire Rozino gold project (“Rozino” or the “Project”), located in southeast Bulgaria.
Results of this work will be incorporated into the Rozino NI 43-101 Preliminary Economic Assessment (“PEA”), which is in progress with results expected to be released in September 2018. Delivery of the PEA is the mechanism by which Velocity will earn a 70% interest in the Rozino gold deposit.
“Comprehensive metallurgical test work has provided us with positive results for inclusion into the Rozino PEA. The results included here provide Velocity with a mechanism to produce a 30 g/t gold concentrate, which is amenable to processing at the nearby Gorubso carbon-in-leach plant,” stated Keith Henderson, Velocity’s President & CEO. “The flotation test work has demonstrated that the process delivers a high-quality concentrate for input to the existing CIL plant. With extremely low sulphide contents, low carbon contents and negligible deleterious elements, this low-volume, high-grade concentrate should complement the development options being considered in the PEA.”
Highlights of Results
- >98% of sulphide recoverable to produce a gold concentrate using standard flotation
- Low-volume, high-grade concentrate complements PEA project development options
- Concentrate produced typically averages 30 g/t gold
- Flotation gold recoveries of approximately 91%
- Extremely simple mineralogy with negligible deleterious elements
- Low sulphide content (<1%) and low mass pull (<5%)
- Low carbon content (1.2%) minimizes pregnant solution robbing during leaching
- Environmentally benign waste tailings product
- Results based on representative bulk sample comprised of 1,600 core samples
Simple Mineralogy at Rozino
The uncomplicated nature of mineralogy at Rozino is one of the attractive features of the gold deposit. The mineralization is very simple with gold associated with pyrite, which is the only significant sulphide mineral in the deposit.
Flotation Test Work
The test work shows that more than 98% of the sulphide is recoverable to produce a basic gold concentrate using standard flotation techniques, conventional flotation reagents and a grind size of 70% passing 200 mesh. The test work concentrate typically averages 30 g/t gold with recoveries of approximately 91%. The economics of the grind sizing and the reagent scheme used in the test work have not yet been optimized, but these results indicate that a simple metallurgical flowsheet is required, which may be refined in the next phase of test work to further enhance the operating cost inputs.
One of the scenarios being considered in the PEA will be trucking of this concentrate to Gorubso’s CIL facility in Kardzhali. The cost of trucking this concentrate to Velocity’s partner is not expected to be material to the economics of the project.
Leach Test Work
Cyanidation tests were carried out on whole-rock mineralized material, at differing grind sizes, and on the flotation concentrate described above, via 48-hour bottle roll test work. The whole rock tests were conducted at 60% and 80% passing 200 mesh with recoveries of 70% and 83% respectively and moderate cyanide consumptions of 2.14 and 2.23 kg/t respectively. Leach kinetics are good with leaching effectively complete within 24 hours.
Best leach results were gained from leach tests on flotation concentrates returning optimum leach times of 24 hours and recoveries of 87% extraction (Table 1). Finer grinding of the concentrate does not appreciably increase the leach recovery.
Table 1 Leach results of gold concentrates from the Rozino deposit
| Extraction | 87.48% |
| Consumption of Na CN | 3.1 kg/t |
| Added NaCN | 7.3 kg/t |
| Consumption of NaOH | 5.0 kg/t |
Bulk Sample Composition
Head grade analyses of the bulk sample concurs with previous gold assay results:
Table 2 Feed analysis of the 130kg bulk sample used for metallurgical test work
| Gold | Sulphur | Carbon | Silver | Copper | Arsenic | Lead | Antimony | Zinc | |
| Bulk Sample Average Head Grade | (g/t) | (%) | (%) | (g/t) | (ppm) | (ppm) | (ppm) | (ppm) | (ppm) |
| 1.28 | 0.42 | 1.20 | 2.0 | 48 | 125 | 28 | <5 | 74 | |
Mineralogical analysis of the bulk sample using X-Ray Diffraction (XRD) confirmed a very straightforward Low Sulphidation Epithermal style of mineralization as outlined in Table 3. Positive aspects include extremely low sulphide contents, low carbon contents and negligible deleterious elements. The very low carbon content will avoid any negative impact on gold recoveries through pregnant solution robbing during cyanide leaching. The very low sulphide content together with very high recoveries of the sulphides (>98%) results in a low mass pull concentrate (<5%) and leaves a waste tailings product that is environmentally benign.
Table 3 Mineralogical composition determined by XRD
| Mineralogy | Weight % |
| Quartz | 61 |
| Mica | 18 |
| Potassium Feldspar | 11 |
| Carbonate | 9 |
| Pyrite | <1 |
All of the gravity and flotation test work was carried out on a 130kg bulk sample assembled from all of the significant drill intercepts from the 2107 and 2018 drill programs. The sample was carefully prepared with material from more than 1,600 core samples.
Velocity has greatly improved on the results of historical metallurgical test work carried out by previous operators at Rozino. In part this improvement can be attributed to the quality of the bulk sample assembled by Velocity and the extent to which it is representative of the deposit.
Gravity Test Work
Gravity test work demonstrated that no significant free gold is being lost and the test work did not improve upon the overall results, even when integrated with the flotation test work. As a result, the gravity option will most likely not be considered in the upcoming PEA.
Ball Mill Work Index
Initial Bond Ball Mill Work Index (“BWI”) determination was carried out on whole drill core and returned a calculated value of 14.52. This work is preliminary in nature and further work including SAG mill test work is required, but the results are sufficient for the initial ball mill design to be incorporated in the PEA. The BWI results are included in Table 4. Preliminary BWI test work was carried out on whole core taken from representative intercepts.
Table 4 Initial Bond Work Index results for the Rozino mineralization
| D80 particle size of the feed | d80 particle size of the end product | End product specific mass | WG* | WI** |
| (mm) | (mm) | (g/rev) | (kWh/g) | (kWh/t) |
| 1.80 | 0.095 | 1.87 | 5.72 x 10-3 | 14.52 |
| * WG | – Energy consumption per g end product | |
| ** WI | – Bond Work Index | |
Details of …read more
From:: Investing News Network