World Placer Journal - 2000 - Volume 1, pages 1-9. | ||
| To conduct a bulk test for placer gold requires care and special knowledge. Here is a good example. | ABSTRACT Bulk testing of the Toson Terrace placer gold deposit in the Zaamar Goldfield of Mongolia was carried out by Golden Tiger Corporation in 1996. The sampling methodology is described, with special attention to determination of the considerable ‘swell factor’ (45-60%) in order to calibrate the results of gold grade for loose material (LCM) with that for ‘in situ’ virgin ground (BCM). The Bulk Testing was by a Pilot Plant with an electric water pump rated to deliver 100m³/hour of water, a 100m suction line and foot valve delivering to an 80mm diameter wire-reinforced quick-coupled flexible delivery line. Material was fed into a 6m³ hopper protected by a 150mm grizzly, and discharged onto an inclined belt conveyor fitted with a Ramsey Weighbridge Belt Scale, giving continuous throughput readings, and fed into a 4m long trommel (incl. 1m scrubber) via a feed chute equipped with water spray to produce a slurry. The trommel screened off oversize at >5mm. The <5mm was pumped to a 75cm KNELSON™ concentrator. The feed slurry was c.40% solids, and the KNELSON™ had a maximum feed capacity of 20m³/hour of solids. Concentrates were collected after each c.100m³ batch sample. Power supply was a 125KVA generator coupled to a Cummins diesel engine, equipped with an electronic control switch panel 220/380 volts. The results indicate a gold grade of 320mg/m³ (‘in situ’ BCM) for a 3m Low Grade Zone, and 415mg/m³ (‘in situ’ BCM) for a 4m thick High Grade Zone. The top 30cm of the underlying bedrock material yielded a gold grade of 317mg/m³ (‘in situ’ BCM). 200m³ of sluice tailings were processed by the Pilot Plant and the KNELSON™ recovered 29.02 grams of gold, indicating a grade of 145mg/m³ (loose material LCM). These tailings were from the High Grade Zone, thus the sluice mining achieved only 51% gold recovery. | |
| THE AUTHOR ... ... Gary Beaudoin. Demonstrating placer gold produced from the Toson Terrace. Read the paper for a detailed account of the bulk test on the Toson Terrace, a typical placer in the Zaamar Goldfield - 40+ placer gold mines are active. | |
 | THE PILOT PLANT... in action on the Toson Terrace. The KNELSON and trommel are clearly visible, on a mobile trailer, fed by a mobile conveyor unit. The feed hopper is in the background. | |
