Services

Gold (Au) Analysis

Fire Assay (FA)

Fire Assay (FA) is a traditional method used to determine Gold (Au), Silver (Ag) and Platinum Group Metals (PGM) content in ores and other materials. The 30-50g sample aliquots are mixed with a flux and placed in a crucible. The crucible is then heated in a furnace at >1000℃. The heat allows the mixture to melt, which results in a lead button at the bottom of the crucible and a slag which ﬂoats on the top. The button contains metals (i.e. Au/Ag) and the slag holds gangue minerals present in the sample. The slag is then separated and the lead button is placed in a cupel where it will be heated again in a separate furnace at 900℃. The lead is oxidized and absorbed into the cupel, leaving behind a precious metal bead. Depending on the concentration, the bead will either be analyzed by ICP-OES or by gravimetric analysis. Samples which are heterogeneous by nature may require Screen Fire Assays to determine fine and coarse gold content, especially, if the ore material contains the nugget effect. In addition to the production Fire Assay facility, AAL has a separate high-grade preparation and FA furnace for samples which have high concentrations of gold. Fire Assay is a reliable and well-established method often used by mining and exploration to determine the economic viability of ore deposit projects.

Our Fire Assay services include:

Cyanide (CN) Digestion

Cyanide Leaching is a hydrometallurgical process often used in mining and exploration programs to extract gold from low-grade ores. In mining, cyanide solution is percolated into ore deposits in vats, columns or heaps. The dissolved gold can later be recovered using a variety of methods. Here at AAL, we take a 15g-50g sample, digest the sample in sodium cyanide (NaCN), then tumble the solution for multiple hours. The solution is then decanted into smaller tubes, centrifuged and read on the ICP-OES. Gold (Au), Silver (Ag) and Copper (Cu) can all be measured at low detection limits. The effectiveness of the digestion can be affected by multiple parameters including temperature, cyanide concentration, pH, etc. If your samples require special handling, our lab can provide specified instructions to adjust for such parameters (see schedule for details). AAL also provides Bulk Leach Extractable Gold (BLEG) and Preg-Robbing. BLEG is often advantageous because it can be used to reduce the impact of nuggety gold due to the larger sample size (1Kg). Preg-robbing digestions are often used for carbonaceous matter in which the samples may remove gold from dissolved solution. This “robbing” effect is measured by comparing a regular leach to a spiked leach. Please contact us to discuss your specific project needs.

Our cyanide services include:

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