Mr. Keith Henderson reports
VELOCITY RECEIVES POSITIVE METALLURGICAL RESULTS AT ROZINO GOLD PROJECT, SOUTHEAST BULGARIA
Velocity Minerals Ltd. has received positive results from comminution, flotation and gravity recovery, and leach testwork on a bulk sample representative of the entire Rozino gold project, located in southeast Bulgaria.
Results of this work will be incorporated into the Rozino National Instrument 43-101 preliminary economic assessment, 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-per-cent interest in the Rozino gold deposit.
"Comprehensive metallurgical testwork 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 and chief executive officer. "The flotation testwork 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:
- Greater than 98 per cent 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 grams per tonne gold;
- Flotation gold recoveries of approximately 91 per cent;
- Extremely simple mineralogy with negligible deleterious elements;
- Low sulphide content (less than 1 per cent) and low mass pull (less than 5 per cent);
- Low carbon content (1.2 per cent) minimizes pregnant solution robbing during leaching;
- Environmentally benign waste tailings product;
- Results based on representative bulk sample consisting 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 testwork
The testwork shows that more than 98 per cent of the sulphide is recoverable to produce a basic gold concentrate using standard flotation techniques, conventional flotation reagents and a grind size of 70 per cent passing 200 mesh. The testwork concentrate typically averages 30 g/t gold with recoveries of approximately 91 per cent. The economics of the grind sizing and the reagent scheme used in the testwork 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 testwork 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 testwork
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 testwork. The whole rock tests were conducted at 60 per cent and 80 per cent passing 200 mesh with recoveries of 70 per cent and 83 per cent respectively and moderate cyanide consumptions of 2.14 and 2.23 kilograms per tonne 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-per-cent extraction. Finer grinding of the concentrate does not appreciably increase the leach recovery.
LEACH RESULTS OF GOLD CONCENTRATES
FROM THE ROZINO DEPOSIT
Extraction 87.48 per cent
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 analysis of the bulk sample concurs with previous gold assay results as shown in the attached table.
FEED ANALYSIS OF THE 130 KG BULK SAMPLE USED FOR METALLURGICAL TESTWORK
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 the attached table. 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 (greater than 98 per cent) results in a low mass pull concentrate (less than 5 per cent) and leaves a waste tailings product that is environmentally benign.
MINERALOGICAL COMPOSITION
DETERMINED BY XRD
Mineralogy Weight %
Quartz 61
Mica 18
Potassium feldspar 11
Carbonate 9
Pyrite <1
All of the gravity and flotation testwork was carried out on a 130-kilogram bulk sample assembled from all of the significant drill intercepts from the 2017 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 testwork 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 testwork
Gravity testwork demonstrated that no significant free gold is being lost and the testwork did not improve upon the overall results, even when integrated with the flotation testwork. 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 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 testwork 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 the attached table. Preliminary BWI testwork was carried out on whole core taken from representative intercepts.
INITIAL BOND WORK INDEX RESULTS FOR THE ROZINO MINERALIZATION
D80 particle size D80 particle size End product WG* WI**
of the feed of the end product specific mass
(mm) (mm) (g/rev) (kWh/g) (kWh/t)
1.80 0.095 1.87 5.72 multiplied 14.52
by 10 to the power
of negative 3
* WG -- Energy consumption per g end product.
** WI -- Bond work index.
Details of flotation testwork results
Fifteen variations of flotation testwork were carried out, including two lock cycle tests using a variety of differing grind sizes and reagents, and the results are included in the flotation testwork table.
The locked cycle testwork was carried out on a coarser grind fraction than most of the other tests and returned an average recovery of 91 per cent within a concentrate grading 30 g/t using standard flotation methodology and relatively low-cost reagents. Finer secondary grinding of the concentrate did not result in significant improvement in recoveries indicating that there is no cost benefit to producing higher-grade concentrates using finer grind processes.
Owing to the efficient recovery and low starting concentrations of pyrite the mass pull is less than 5 per cent resulting in a low-volume concentrate with high gold recoveries.
SUMMARY OF FLOTATION TESTWORK ON THE ROZINO BULK METALLURGICAL SAMPLE
Test Grind % -75 micron Reagents Recoveries
Na2CO3 (g/t) KIBK (g/t) Aero 242 (g/t) BM (g/t) Au (g/t) Au (%)
1 80 850 25 25 100 23.35 89.17
2 50/80 850 50 * 10 27.71 85.10
3 90 850 25 25 50 17.0 88.19
4 50 850 25 25 25 19.80 60.65
5 Ex grav 2 850 25 25 25 37.50 53.75
6 80 850 25 25 50 16.37 87.67
7 70 850 25 25 50 21.93 87.81
8 80 850 75 0 50 35.49 86.24
9 80 850 25 25 50 22.20 85.98
10 80 850 KXK 100 0 25 21.96 80.37
11 LCT# 70 850 25 25 25 36.40 90.66
12 LCT# 70 850 75 0 50 24.10 91.45
13 60 850 50 50 50 24.15 82.84
14 70 250 50 50 75 18.96 88.03
15 70 0 0 50 75 24.49 86.14
* NaHS and CuSO4 to mill.
# LCT locked cycle tests.
Quality assurance/quality control
The metallurgical work program at Rozino was designed and is supervised by Len Holland, BSc, CEng, FIMMM, FMES, an independent consulting metallurgist who is responsible for all aspects of the metallurgical testwork, including the quality control/quality assurance program.
The flotation, gravity and leach testwork, together with gold deportment, mineralogical and laser sizing studies were carried out by Eurotest Control EAD, Bulgaria, on a homogenized bulk sample that was assembled through splitting of 1,632 coarse reject samples. The sample splitting was carried out by Velocity's staff using Jones splitters in accordance with best international practice. The bulk sample was subsequently homogenized by Eurotest according to the Australian Standard -- AS 3988-91 -- Sample Preparation for the Determination of Gold, before being divided into one kg aliquots using a rotary splitter. Eurotest conducted homogenization tests including Fischer dispersion analysis and 50 chemical analyses in order to ensure that each metallurgical sample was representative of the combined mineralized intervals from Rozino.
The Eurotest Control laboratory is certified by LRQA to ISO 9001. The company also holds a certificate of accreditation as a testing laboratory pursuant to BDS EN ISO 17025. Analyses of materials less than five grams per tonne gold were carried out by ICP-OES on aqua regia digest. Samples containing more than five g/t were analyzed by 30 g fire assay using an AAS finish. Specialist determinations were carried out in accordance with best international practice, for example sulphur was determined by the LECO technique. Comminution studies were carried out by Eurotest and the University of Mining and Geology in Sofia. The preliminary BWI determination was carried out on a 22.5 kg sample of whole drill core selected to be representative of typical mineralization from the Rozino deposit.
Qualified person
The technical content of this release has been approved for disclosure by Mr. Holland, a qualified person as defined by National Instrument 43-101. Mr. Holland is independent of the company.
About the Rozino gold project
Velocity has been exploring and drilling at Rozino since August, 2017, publishing a maiden inferred mineral resource estimate in Q1 2018: 17 million tonnes of 1.15 grams per tonne gold for 629,000 ounces at a 0.5-gram-per-tonne cut-off grade with 8.2 million tonnes of 1.68 grams per tonne gold for 443,000 ounces at a 0.8-gram-per-tonne cut-off grade. Approximately 90 per cent of estimated resources at depths of less than 110 metres from surface and less than 1 per cent below 150 metres from surface. Mineralization remains open for expansion.
The company has completed the 2018 drill program with a view to publishing an updated mineral resource estimate and PEA before year-end. On completion of the PEA, the company will exercise its option for a 70-per-cent interest in the project and will move forward in joint venture with its Bulgarian partner.
About Velocity Minerals Ltd.
Velocity is a gold exploration and development company focused on Eastern Europe. The company's management and board includes mining industry professionals with combined experience spanning Europe, Asia and the Americas as employees of major mining companies, as well as founders and senior executives of junior to mid-tier public companies. The team's experience includes all aspects of mineral exploration, resource definition, feasibility, finance, mine construction and mine operation as well as a record in managing publicly listed companies.
We seek Safe Harbor.
© 2024 Canjex Publishing Ltd. All rights reserved.