Direct smelting (Borax)

The process involves direct smelting of the gold concentrate to produce a doré. Smelting can be done with any flux, however Borax (sodium tetraborate) is the most commonly used. To start the process, clean concentrate is mixed with borax and water in a plastic bag, which is then placed into a crucible. Once in the crucible, it is heated with charcoal and a gas torch. Portions of borax are added into the crucible as heat is applied. This is so that, borax lowers the melting point of the mineral impurities in the concentrate to separate them from gold. The process can also be carried out using a furnace. With this route, a crucible with the concentrate and flux are place inside the furnace. After heating the crucible, the molten concentrate is poured into a cupel. The gold will sink to the bottom with a layer of impurities at the top. Once it has cooled and hardened, the slag is crushed with a hammer to release the gold bead (Telmer and Stapper, 2012).

Direct smelting (Borax) - Technology Assessment

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Categories Sub-categories Assessment questions Assessment
Properties of the ore Type of deposits Is the technology suitable for hard rock deposits? None
Is the technology suitable for alluvial gold deposits? Yes
Is the technology suitable for eluvial gold deposits? None
Type of ore Is the technology suitable for free milling ores? Yes
Is the technology suitable for oxide ores? None
Is the technology suitable for sulphide ores? Yes
Is the technology suitable for carbonaceous ores? None
Is the technology suitable for refractory ores? None
Is the technology suitable for sand rock bearing ore? None
Is the technology suitable for ore with clay material? None
Is the technology suitable for ore bearing nuggets? None
Is the technology suitable for ore in desert areas? None
Is the technology suitable for ore in wet conditions? None
Is the technology suitable for ore in coarse gravels? None
Is the technology suitable for ore in fine gravels? None
Grade/gold content Is the technology suitable for high grade ores? Yes
Is the technology suitable for low grade ores? No
Grain size of the gold) Is the technology suitable for fine grained gold? Yes
Is the technology suitable for course grained gold? Yes
Is the technology suitable for mixed fine and course material? None
Is the technology suitable for very/ultra fine grained gold? No
Feed volume (batch volume) Is the technology suitable for large quantity of feed material? No
Is the technology suitable for small quantity of feed material? Yes
Operationals requirements Cost of equipment Are the costs of procuring the technology affordable to artisanal miners? Yes
Are the costs of procuring the technology affordable to small-scale miners? Yes
Are the costs of operating the technology affordable to artisanal miners? No
Are the costs of operating the technology affordable to small-scale miners? None
Are the costs of maintanance and replacement affordable to small-scale miners? None
Are the costs of maintanance and replacement affordable to artisanal miners? None
Utilities and inputs required Does the technology require water? None
Is the amount of water required suitable to processing by individual miners? None
Does the technology require electricity or power source? Yes
Is the amount of electricity required suitable to processing by individual miners? None
Does the technology requre diesel? No
Is the amount of diesel required suitable to processing by individual miners? None
Does the technology require reagents during processing? Yes
Is the amount of reagents suitable for processing by individual miners? None
Does the technology require any other infrastructure? None
Type of organisation Does the technology allow operation by individual miners? Yes
Does the technology allow operation by group of miners? No
Does the technology allow operation by organisations? No
Does the technology allow operation by processing plants? No
Does the technology work only with a continous system? No
Does the technology work with batch and continous systems? No
Does the technology work only with a batch system? Yes
Processing flowsheet and performance of the techology Processing flow Does the technology work as a standalone? Yes
Does the technology work as part of a process system? Yes
Gold recovery Does the technology offer high recovery rates compared to the amalgamation process? Yes
What are the typical gold recoveries for this technology? 98%
Does the technology produce gold directly? Yes
Does the technology produce gold directly but in a different form to be converted to gold? No
Does the technology require other processes to recover the gold? No
Are there potential gold losses during processing with this technology? None
Processing time Does the technology offer less processing time compared to the amalgation process? None
Tailings Can the technology re-process tailings? None
Recovery of other minerals Can the technology recover other minerals in addition to gold? None
Visual tracking and monitoring Does the technology allow visual tracking and/or monitoring? Yes
Local considerations Availability of the equipment Does the technology make use of equipment that is locally available? Yes
Availability of the inputs Does the technology require inputs that can be locally sourced? Yes
Scalability of the technology Can the technology be scaled up or down to suit the spectrum of ASGM activities? No
Adaptability of the technology Can the technology be used in remote areas? Yes
Ease of use/learning (skills requirement) Is the technology easy to use or learn? No
Does the technology require knowledge /skills on metallurgy to use? Yes
Capacity to maintain Is the technology easy to maintain? Yes
Health, safety and environment Risks Health and safety hazards Does the recovery of gold using this technology pose any health and safety hazards? Yes
Environmental risks Does the recovery of gold using this technology pose any environmental risks? No

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3 comments have been posted about this technology

    markus wormwood - March 15, 2024, 1:58 p.m.
    is this like the furnace from minecaft as i would like to cook some raw horse i mined earlier best regardations markus

    Reply
    Herobrine Minecraft - March 15, 2024, 2 p.m.
    Shalom markus, this is the furnace developed in israel which is very good for raw horses that you have mined with a pickaxe. Best regards, Rabbi Herobrine

    Steve . - March 15, 2024, 2:02 p.m.
    this is a reply to rabbi herobrine: as a person from minceraft myself i would know that the blast furnace is best in terms of cooking raw horse if you were looking to smelt some gold that would be the smoker