The 2015 resource update for Golden Band's Bingo deposit includes a brief description of the Jolu Mill circuit used while the Roy Lloyd mine operated: two-stage crushing, ball milling to 70% passing 140 microns, Knelson gravity concentration and cyanide leach with carbon in pulp.
Bingo is a gold deposit in the La Ronge gold belt of northern Saskatchewan, about 95 road-kilometres north-northeast of La Ronge and 15 km north of the community of Missinipe. A 3.5 km gravel mine haul road gives access. Golden Band Resources Inc., a former gold producer, owns the property 100%. CanMine Consultants prepared the NI 43-101 technical report and mineral resource estimate update, with an effective and signing date of November 3, 2015. The report's recovery methods section is short and historical. It states that the project was shut down in early 2014 and has reverted to a resource disclosure, so the description of the mill applies to the period when the Roy Lloyd mine was in operation and is no longer current.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Crushing stages | 2 | Not applicable | Jaw crusher and cone crusher |
| Screen opening | 2 | in | Oversize to cone crusher |
| Fine ore bin | 400 | t | Capacity |
| Ball mill grind | 70 | % passing 140 µm | Closed with classifying cyclones |
| Gravity concentrator | Knelson | Not applicable | On coarser cyclone fraction |
| Intensive leach | Acacia reactor | Not applicable | Semi-continuous |
| Leach tanks | 4 | stages | 50% solids by weight |
| Leach residence time | 48 | hours | Design |
| CIP stages | 6 | Not applicable | Carbon flows counter-current |
| Indicated resource | 268,183 | t at 9.60 g/t Au | 5 g/t cut-off |
| Inferred resource | 194,634 | t at 11.47 g/t Au | 5 g/t cut-off |
| Property area | 2,154 | ha | 1 mineral lease and 2 claims |
Overview
The mill that treated Bingo ore had a two-stage crushing plant and a milling circuit with both gravity recovery and carbon-in-pulp (CIP) circuits. Coarse gold was recovered by gravity and intensive leaching, and the finer cyclone fraction went to cyanide leaching and CIP. Gravity and leach streams were linked, since gravity and Acacia tailings were recirculated to the ball mill so that unrecovered fine gold would report to leaching and CIP.
Key Process Stages
Crushing
A loader fed run-of-mine ore to a grizzly and, through a pan feeder, to a jaw crusher. Jaw crusher product went to a vibrating screen with a 2 inch opening. Material coarser than 2 inches flowed to a cone crusher for secondary crushing, and the product recirculated to the screen. Finer material went to a 400 tonne fine ore bin that supplied the mill.
Grinding and gravity recovery
Ore from the fine ore bin went to a ball mill that ground it to 70% passing 140 microns. The slurry was pumped to classifying cyclones. The coarser fraction, roughly plus 140 microns, went to a Knelson concentrator, which centrifugally concentrated a rich gold concentrate. The concentrate was exposed in a semi-continuous process to an accelerated leach in an Acacia reactor. The gold-rich pregnant solution was treated in electrowinning cells ahead of smelting. Tailings from the concentrator and from the Acacia reactor were recirculated to the ball mill.
Leaching and carbon in pulp
The finer cyclone fraction went to a thickener and then to a four-stage cyanidation operation. Slurry was delivered to the leach tanks at 50% solids by weight, and the design residence time was 48 hours. Continuous leach discharge flowed by gravity to a six-stage CIP operation, with carbon moving counter-current to the slurry by pneumatic transfer. Slurry went to tailings continuously after CIP. Loaded carbon was collected and, in batches, sent to a stripping vessel where a pregnant solution was eluted. A parallel electrowinning cell treated this solution ahead of smelting.
Mill performance and history
The Jolu Mill processed run-of-mine ore from the Bingo deposit from January 2011 until January 2014, often blended with ore from other deposits, including the EP pit, the Komis open pit and Golden Heart. Before commercial production, metallurgical testing indicated that about two-thirds of the gold in Bingo material could be recovered readily by gravity. Cyanidation of the gravity tailings suggested that a 48 hour leach at a grind of 82 to 96 microns could extract 91% to 95% of the remaining gold, and overall recoveries from gravity and cyanidation ranged from 97.3% to 98.2%. At production scale, up to 80% of the gold was recovered by gravity, and overall recovery was about 96% when processing Bingo ore exclusively. During commissioning, overall recovery dipped to 92.5% and improved as the operation matured.
Production mining through the Roy Lloyd mine began officially on April 1, 2011 and had extracted 121,131 tonnes of ore with a recovered 48,907 ounces, averaging 12.6 g/t gold, by December 31, 2012. The company later reported a further 73,263 tonnes at 7.51 g/t gold and announced an indefinite suspension of operations in January 2014.
Additional Interesting Data and Summary
The history of the deposit helps place the mill. Uranerz Exploration and Mining acquired the Dickens West joint venture with Cameco in 1991 and discovered the Bingo showings in 1992. Golden Band acquired the property in 2002, and approved a production decision for the Bingo gold deposit and the startup of the Jolu Mill on September 2, 2010. Since 1991, 290 exploration drill holes totalling 47,260.8 m have been completed on the property.
The Bingo structure is an intensely mylonitized, quartz-rich shear zone, averaging about 1.5 to 2.0 m wide, with a known strike length of around 450 m. Gold shows a significant nugget effect and is typically associated with pyrite and pyrrhotite and minor chalcopyrite. The 2015 update takes account of mined areas and 100 new exploration drill holes since the May 2009 update, and reports Indicated resources of 268,183 tonnes at 9.60 g/t gold and Inferred resources of 194,634 tonnes at 11.47 g/t gold at a 5 g/t cut-off.
Key Processes
- Jaw and cone crushing with 2 inch screening
- Ball milling in closed circuit with classifying cyclones
- Knelson gravity concentration
- Acacia intensive leach with electrowinning
- Four-stage cyanide leaching
- Six-stage carbon in pulp with batch stripping
Source: NI 43-101 Technical Report and Mineral Resource Estimate Update, Bingo Gold Deposit, Roy Lloyd Mine Project Area, Dickens Lake, Saskatchewan, November 3, 2015.
