SGS MINERALS SERVICES – T3 SGS 218 09-2013
FIRE ASSAY GOLD
ANALYTICAL SERVICES PRECIOUS METAL EXTRACTION INDUCTIVELY COUPLED PLASMA-ATOMIC Once the button is separated from the EMISSION SPECTROMETRY (ICP-AES) Fire assaying is the industry standard gangue, the precious metals are extracted •• The aqueous sample is aspirated process for obtaining analytical gold from the collector through a process into the plasma and the gold and platinum group element (PGE) data called cupellation. Once the button has contained in the sample emits light from high grade ores. It is a modernized cooled, it is separated from the slag and at characteristic wavelengths. The process but in its simplest form, has been cupelled. intensities of the emitted light are in use for centuries. Fire assaying is used measured and compared by software in the determination of gold in all sample •• When lead is used as a collector, the to those of standard gold-bearing types, including drill core, soil and chip lead oxidizes and is absorbed into the solutions. The software then samples. cupel leaving a precious metal bead. The bead is then dissolved in aqua calculates the gold concentration in regia for analysis. the sample. •• When nickel is used as a collector, the button is crushed and dissolved INDUCTIVELY COUPLED PLASMA-MASS in hydrochloric acid and the residue SPECTROMETRY (ICP-MS) is filtered to remove extraneous •• The gold contained in the aqueous material, leaving the precious metal sample is ionized. The intensity of the residue on the filter. signal at mass 186 is measured, as well as the signals of any potentially interfering isotopes. The intensity at 186µ is measured and compared by software to those of standard gold- bearing solutions to determine the concentration of gold in the sample.
INSTRUMENTAL NEUTRON ACTIVATION ANALYSIS (INAA) •• The residue is extracted from the filter paper and irradiated in the core ANALYSIS AND DETECTION of a nuclear reactor. Most elements become radioactive and emit gamma- Gold and PGE can be analyzed by several ray radiation of specific wavelengths. methods: THE PROCESS The wavelengths of gold are measured and compared against FUSION FLAME ATOMIC ABSORPTION (AA) gold standards to determine the concentration of gold in the sample. The pulverized sample is weighed •• The sample is dissolved in aqua and mixed with a fluxing agent. The regia and then aspirated in an flux assists in melting, helps fuse the acetylene flame. A beam of light at sample at a reasonable temperature a wavelength matching that of gold and promotes separation of the gangue is passed through the flame. The material from the precious metals. In gold in the sample absorbs the light addition to the flux, lead or nickel is added proportionately depending on the as a collector. The sample is then heated concentration of the element in the in a furnace where it fuses and separates solution. The absorption is compared from the collector material ‘button’, which to standard solutions to determine contains the precious minerals. gold concentration in the sample. SGS MINERALS SERVICES – T3 SGS 218 2
SCREENED METALLICS LIMITS OF DETECTION CONTACT INFORMATION Gold by screened metallics fire assay •• 30g = ½ assay tonnes Email us at [email protected] consists of screening 500g of the sample •• 60g and 90g assays are available www.sgs.com/mining to 106 microns. The plus fraction is fire upon request assayed for gold and a duplicate assay is performed on the minus fraction. The size fraction weights, coarse and fine fraction gold content and total gold content are reported.
GOLD BY LEAD COLLECTION FIRE ASSAY/INSTRUMENT FINISH TRACE LEVELS LIMITS FAA 313 Gold by Fire Assay, AAS, nominal weight 5ppb-10,000ppb 30g FAI313 Gold by Fire Assay, ICP-AES, nominal 1 ppb - 10,000 ppb weight 30g FAI515 Gold by Fire Assay, ICP-AES, nominal 1 ppb - 10,000 ppb weight 30g ORE GRADE FAA303 Gold by Fire Assay, AAS, nominal weight 0.01 ppm-100 ppm 30g FAG303 Gold by Fire Assay, gravimetric, nominal 3 g/t weight 30g FAG505 Gold by Fire Assay, gravimetric, nominal 3 g/t weight 50g FAG323 Gold and silver by fire assay, gravimetric, 3 g/t, 5 g/t weight 30g © SGS Group Management SA – 2013– All rights reserved - SGS is a registered trademark of SGS Group Management SA