Column Leach Testwork Confirms High Gold Recoveries From Cyclopic Area
VANCOUVER - Gold Basin Resources Corporation reported on the column leach Metallurgical Testwork conducted by Kappes Cassiday & Associates (KCA) in Reno, Nevada on diamond core samples from the Cyclopic area of the Gold Basin project in Mohave County, Northern Arizona. Results are: 1) Gold extractions up to 80% (after 67-72 days of leach) on Cyclopic diamond core composite samples. Gold extractions between 50 and 70% after 7 days in leach. 2) Agglomeration and compaction tests showed all agglomerated samples passed percolation tests up to 100 meters dump height (KCA standard height recommendation is 40 meters). 3) Gold Basin mineralization extremely low in preg-robbing soluates and less than 0.61% total carbon in the material. 4) All results show low reagent consumption in leach.
All results indicate Gold Basin mineralization is a rapid leaching material with low preg-robbing characteristics that when agglomerated passes industry criteria for flow rates for dump heights up to 100 meters.
CEO Mike Povey, said, “We are pleased with this initial set of metallurgical testwork results that demonstrate strong recoveries that are indicative of a broad range of heap-leach projects in the SW USA. In consultation with KCA, we expect future optimization testwork to begin evaluating coarser crush opportunities as we continue to focus on extending the mineralization and thus increase ore samples for further composites. The results are an excellent start and confirm there are no metallurgical barriers to a heap-leach gold extraction operation at Gold Basin.”
Further to the positive initial Bottle Roll leach testwork completed in late 2021 further metallurgical studies have been undertaken in order to determine additional parameters on the heap leach suitability of the Gold Basin mineralization. As preparation for these studies the Company drilled four (4) PQ core diamond drillholes at 200 meters intervals along strike at the Cyclopic deposit during the 2021 resource drilling program. This drillhole interval sequence and depth of hole was determined to provide a sufficiently representative mineralized samples for the planned testwork.
The core samples were delivered to KCA’s laboratory facilities in Reno, Nevada on the 6th December 2021 and the metallurgical program of work was undertaken between December 2021 and May 2022 included column leach and agglomeration / compaction testwork as well as some additional bottle roll tests.
In order to evaluate the relative effects on gold extraction both conventional crushing and High Pressure grinding roll (HPGR) crushing methodology was used to prepare the diamond core material for the column leach and agglomeration tests.
Under reagent in the column leach all samples showed a rapid extraction response to the reagent solution with gold recoveries between 52% and 70% being achieved after only 7 days of leaching. Each sample was progressed to where the leaching had effectively plataued and provided: 1) Column leach gold extractions of 75% and 71% on conventional crushed composite samples after 72 days of leach period. 2) HPGR crushing resulted in an increased gold extractions of 80% and 78% after 67 days of leach.
Preliminary agglomeration and compacted permeability test work was conducted on portions of the conventionally crushed material and HPGR crushed material from each composite sample. The purpose of the percolation tests was to examine the permeability of the material under various cement agglomeration levels (0, 2, 4 and 8 kilograms per metric tonne of Portland Type II cement. All samples tested passed the KCA criteria for flow rate with the exception of HPGR crushed Composite 1 (KCA Sample No. 93148 A) that had no cement addition. The purpose of the compacted permeability test work was to examine the permeability of the crushed material, agglomerated at various cement levels, under compaction loading equivalent to heap heights of 20 and 100 meters of overall heap height. Both the conventional crushed material (agglomerated with 2 and 5 kg/MT cement) and the HPGR crushed product (agglomerated with 4 and 8 kg/MT cement) for Composite #1, failed at an equivalent heap height of 100 meters due to low solution flow rate and/or excessive slump. The HPGR crushed product (agglomerated with 2 kg/MT cement) for Composite #2, failed at an equivalent heap height of 100 meters due to low solution flow rate. KCA’s general recommendations for heap leach dump heights are a maximum of 40m
Shake tests were conducted on portions of the pulverized head material to provide preliminary indications of soluble metal extractions as part of the testwork process.
In order to investigate the preg-robbing characteristics of the Cyclopic material (often a result of carbonaceous inclusions in particular) additional shake testing was conducted. For these preg-robbing tests, pulverized portions of head material were leached by the same method as the initial shake tests with the addition of a known quantity (spike) of gold in solution. Preg-robbing tendency was then determined by comparing the spiked shake test extraction and the original shake test extraction with the gold spike (original extraction + gold spike). Preg-rob% = 100% – ((Spiked Shake Ext.)/(Shake Ext. + Spike)×100%). If the spiked shake test extraction was lower than the shake test + spike more than 10%, the shake was considered preg-robbing. Differences less than 10% were Differences less than 10% were attributed to variations in the material.
In addition to preg-robbing tests a number of additional Head analyses were carried out which included analyses for multi-element, mercury and copper, carbon and sulphur (which included to total carbon and sulphur analyses, speciation for organic and inorganic carbon and speciation for sulphide and sulphate sulphur). Of note the total carbon was found to be less than 0.61% and total sulphur insignificant at less than 0.01%.