Cyanide leaching was first applied to extract gold from pyritic ore, which prior to the discovery of gold cyanidation could not be extracted. This led to heavy investment in mining in the 1890s and the opening of larger gold mines. Leaching gold with cyanide is still a widely used hydrometallurgical process in today's mining industry. Cyanide methods are applied to samples from many stages of the mining cycle. These methods can be used in exploration on large-sized soil or sediment samples to identify anomalies, or drill samples with known mineralisation to identify cyanide soluble minerals.
Cyanide leaches are a routine analytical method used during resource drilling as a first pass estimation of how an ore will behave during cyanide hydrometallurgical processing. ALS has a number of method options available for cyanide leach with AAS finish.
Code | Analyte | Range (ppm) | Description |
---|---|---|---|
Au-AA13 Ag-AA13 Cu-AA13 |
Au Ag Cu |
0.03-50 0.03-350 0.1-2,000 |
Au, Ag, Cu by cyanide leach with AAS finish. 30g sample |
Au-AA14 | Au | 0.01-200 | Au by cyanide leach with AAS finish. 12hr Leach. Up to 1kg sample |
Au-AA15a Au-AA15b Au-AA15c Au-AA15d |
Au | 0.001-125 | Au by accelerated cyanide leach using LeachWELL Assay Tabs™ with AAS finish. 4hr Leach. 500g sample request Au-AA15a For 1kg request Au-AA15b For 2kg request Au-AA15c For 3kg request Au-AA15d |
Au-AA31 Au-AA31a |
Au | 0.03-500 | Au Preg Rob Leach with Gold Spike. Au Preg Rob Leach without Gold Spike. 10g sample per method |
For gold exploration, cyanide leaches can be used to analyse soils and sediments to levels below crustal abundance. Cyanide leach provides ALS's lowest gold detection limit which is possible due to the stability of gold cyanide complexes coupled with ICP-MS instrumentation optimised for gold sensitivity. Cyanide leaches have lower matrix effects and lower dilution factors compared to aqua regia digestion, which enables detection levels for gold to be five times lower.
Code | Analyte | Range (ppm) | Description |
---|---|---|---|
Au-CN43™ Au-CN44™ |
Au | 0.02ppb-1ppm | Au by cyanide extraction with ICP-MS finish. 25g sample Au by cyanide extraction with ICP-MS finish. 50g sample |
Cyanide is used in bulk leach extraction methods which are designed to overcome nugget effect in the sampling of gold bearing materials.
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