Analysis
A large quantity of sample (between 2 and 5 kg) is digested or leached with cold sodium cyanide (NaCN) solution (generally 0.1% NaCN), for one to several days (depending on the assay laboratory involved). The gold is dissolved through its formation of a cyanide complex, which is concentrated through the solvent exchange process into an organic solvent and subsequently analyzed. The use of large sample weights and solvent extraction enables low detection limits, as low as 0.1 ppb. The digest is analyzed for Au (0.01 ppb), Cu (0.01 ppm), Ag (0.5 ppb), and depending on situations, for other elements. However, gold values in BLEG are lower than total assays such as those of fire assays, as it analyzes only the fine grained gold fraction and largely ignores coarser and nuggety gold.
If the need arises, a separate split of the original sample is used for pathfinder elements.
Read more about this topic: Bulk Leach Extractable Gold
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