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SGS is a world leader in accurate cyanide extractable gold analysis.


Bulk leach extractable gold (BLEG) is a partial extraction procedure that involves leaching of large (30gm to 2,000gm) samples for geochemical purposes. This robust, “fit-for-purpose” technology is provided at many locations through SGS’s worldwide laboratory network. It addresses challenges related to accurately measuring coarse grained gold and related nugget effect or heterogeneity.

This cost-effective procedure requires minimal sample preparation. Typically, this is only the removal of large pieces of rock. During a BLEG analysis, a large quantity of your sample is digested, or leached, with a cold cyanide solution for one to several days. The gold in the sample is dissolved as cyanide complexes. The leachate is then concentrated in a solvent exchange type procedure and analyzed by AAS or ICP.

SGS bulk leach extractable gold methods include:

Method name Method range Sample size, Leaching interval, Finish
BLE 643 Au 0.03 ppm – 100 ppm 30g, Mini Cyanide Leach, AAS Finish
BLE61K Au 0.01 ppm – 1, 000 ppm 500gm, Active Cyanide Leach; 24 Hour Solvent Extraction, AAS Finish
BLE61N Au 1 ppb – 10,000 ppb 2000gm, Active Cyanide Leach, 24 hour Solvent Extraction, AAS Finish
BLM61K Au 0.05 ppb – 10,000 ppb 500gm Active Cyanide Leach, 24 Hour Solvent Extraction, ICP-MS Finish
BLM61N Au 0.05 ppb – 10,000 ppb 2000gm Active Cyanide Leach, 24 Hour Solvent Extraction; ICP-MS Finish
BLM62N Au 0.05 ppb – 10,000 ppb 2000gm, Static Cyanide Leach, 24 Hour Solvent Extraction, ICP-MS Finish

The large sample sizes and solvent extraction technology used in bulk leach extractable gold analysis provides detection limits as low as 0.1 ppb. The precision of BLEG test results is high due to the large sample size. However, this method is not a total assay and does not compare to fire assay methodology. Gold values in BLEG are lower than those obtained through fire assay.

SGS is a world leader in geochemical analysis. The results from tests conducted in our laboratories have gained international acceptance.

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