Meritus Test Yields 94.3% Au Recovery At Toordogiin
2013-02-26 11:54 ET - News Release
Mr. Terence Bates reports
MERITUS MINERALS RECEIVES POSITIVE RESULTS FROM PRELIMINARY METALLURGICAL TESTS OF PRIMARY ORE AT THE GUTAIN DAVAA PROJECT
Meritus Minerals Ltd. has received the results of preliminary metallurgical testing of the primary mineralization from the Toordogiin Shil prospect at Gutain Davaa. A series of tests including gravity, cyanide leach and flotation was carried out. The initial results indicate that:
- with fine grinding to 100% passing 150 microns up to 91.6% of gold content was recovered using a 24 hour leach in cyanide solution;
- from an 80% passing 75 micron grind flotation tests recovered up to 92% of gold content into a concentrate .Recovery from the concentrate was up to 94.3% of gold in the concentrate in 12 hours; and
- gravity tests results are disappointing due to the fine particle size of the gold.
The laboratory considers additional detailed work may result in an improvement in both leach and flotation gold recoveries
Methodology
The test work was carried out by Vismutin Co Ltd in their laboratory in Ulaan Baatar, Mongolia. After grinding and homogenizing the composite sample the following test work was undertaken:
- Fire assay and multi element analysis by ICP and XRF of two samples (Head Assays 2x 1kg)
- Mineralogical studies ( 1 sample 1kg)
- Bond Impact Crushing Work Index test ( 8 specimens of core)
- Bond Ball Mill Work Index Determination ( 9 samples )
- Grinding time determination ( 4 x 1kg samples)
- Gravity recovery of gold ( 2 samples X 10kg)
- Hydrometallurgical tests - cyanide leaching ( 8 x 1kg samples)
- Batch flotation tests (12 samples x 1kg)
- Preparation and Head Grade
Mineralized intervals were chosen from residual half HQ core to duplicate as close as possible head grade to the head grade registered with the Mongolian Mineral Resource Council, ie 5.73 gAu/t.
A total of 11 separate intersections totaling 50.5 metres from eight holes below the level of oxidation were selected from the Toordogiin Shil deposit. The samples had a total weight of approximately 150 kilograms.
At the laboratory drill core was crushed and screened to 100% passing 2 mm. Crushed ore was then mixed in a homogenizer and triple rotary split to blend the composite. The homogenized sample was then split through a rotary splitter into a number of 1 kg samples for test work. Where necessary the one kilogram sub samples were combined to form larger samples. (i.e. for the gravity test work).
Two one kilogram samples were used to establish the head grade of the bulk sample and in addition were subject to ICP scan and XRF to determine the content of other elements. The gold head grades returned from the two samples were 6.96 and 6.51 gAu/t.
The table below shows the weighted average gold grade of the bulk sample and the individual intersections used to form the bulk sample as determined from the initial assays previously reported by Meritus, and the average grades of the same intersections used by the Resource Consultant to register the deposit. The differences in the two sets of figures for the intersections are due to the Resource Consultant cutting all individual high assays to 30 gAu/t.
Hole No. From To IntersectionWidth m Gutain Davaa LLCAssay, Aug/t Resources ConsultantAssay, Aug/t TSD002 52.00 61.80 9.90 4.06 4.00TSD013 62.60 67.00 4.40 18.15 12.80TSD017 92.00 95.25 3.25 3.60 3.40TSD017 100.00 102.00 2.00 2.92 2.90TSD020 57.45 64.00 6.55 3.55 3.40TSD023 115.20 117.10 1.90 10.45 10.50TSD026 82.60 88.25 5.64 11.64 8.30TSD026 122.70 126.00 3.30 9.44 7.80TSD032 86.50 89.00 2.50 3.71 3.50TSD032 99.00 102.15 3.15 6.74 6.60 TOTAL 50.50m 6.97gAu/t 5.96gAu/t
The average of the two head grade samples, 6.74g Au /t closely approximates the average uncut bulk intersection grade calculated from the uncut sample intervals. The ICP and XRF assays did not reveal the significant presence of any deleterious elements.
Gravity Tests
Two ten kilo composites were used for gravity separation tests. Gravity concentrates from eight different screens ranging from 2 mm down to 106 microns were separated in a Knelson Concentrator. Assays of concentrate and light fraction were carried out for each screen. Results were disappointing as only 24% of the gold was recovered.
Direct Cyanide Leach Test Work
Cyanide leach test work was carried out in rolling bottles. Industrial lime (60% available CaO) was added to establish pH of 10.5 prior to the addition of cyanide to achieve 250 ppm concentration. Gold in solution was checked at 2, 12and 24 hours at eight sieve sizes. Recoveries up to 82.4% are achieved with samples passing 150 microns with a 12 hour leach and up to 91.6% with a 12 hour leach.
Batch Flotation Testwork
Six (6) 1 kg samples were ground to 80% passing 150 microns and six (6) 1kg samples were ground to 80% passing 75 microns. In all samples slurry density was kept at 33%. Methyl isobutyl carbinol (MIBC) was used as a frothing agent and ground rock lime used to control pH at 8, 9.5 and 11. Two collectors, PAX (potassium amyle xanthate) and Aerophine3418A (C8H18PS2), were tested. Rougher flotation time and scavenger flotation time were both three minutes. Due to the small size of scavenger concentrates both the rougher and scavenger concentrates were combined for assay. Highest recovery of 92% was obtained when pH was 11, grind size 80% passing 75 microns and Aerophine was the collector.
Hypochloride Leach
Combined flotation concentrate residues were split into three samples which were leached in a solution with a 7.5% concentration of sodium hyperchlorite and 15% hydrochloric acid. A 12 hour leach time recovered 94.35% of gold in concentrate.
Meritus is encouraged by the results which indicate two different metallurgical processes will achieve acceptable recoveries of gold from the Toordogin Shil gold deposit. The laboratory anticipates that more detailed work is likely to see recoveries improved from what are already acceptable levels.
On a different subject Meritus advises that Mr. Gordon J Fretwell has resigned from the Board of Meritus effective February 25, 2013 due to pressure of other commitments. Mr. Fretwell will continue to serve as Company Secretary and Legal Counsel and hence will maintain his involvement with Meritus. Mr. Fretwell has served as a director since formation of the company and his efforts on our behalf have been much appreciated by the Board. We wish him well in his future activities and look forward to his ongoing contribution to our corporate activity.
For the purpose of this release the qualified person is Terence E Bates MSc. (Geology) the company's Chief Executive Officer and President. All technical information in this release has been compiled or reviewed by Mr Bates . Mr Bates is a fellow of The Australasian Institute of Mining and Metallurgy and is a qualified person as defined by NI 43-101
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