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Specific Gravity and Bulk Density Density is a fundamental rock property and can be defined a number of different ways. At SGS, we determine the specific gravity (SG) and bulk density (BD) of rocks, ores and aggregates. Specific gravity is the density of a material relative to water or air and is expressed as a dimensionless number. It is normally measured by the gas pycnometer method on pulp samples and amounts to the average SG of the mineral particles making up the rock or ore. It is an important parameter when developing metallurgical flowsheets or calculating the exact weight of a concentrate being shipped or stored. Density profiles of ores for dense media separation can be measured using heavy liquids. Bulk density is the average SG of the minerals comprising a rock plus the void space (from vugs, pores, etc.) and is measured by the water immersion method on fist sized rock samples or core. Samples are waxed if there is significant porosity. If the rock samples are competent waxing may not be necessary. Bulk density along with grade and volume is an extremely important parameter in calculating tonnages for Mineral Resource estimates or ore reserves, which are critical for economic evaluation of mineral deposits. Inadequate BD measurements are often at the root of errors in ore estimates with financial consequences for projects. Use high quality specific gravity, bulk density and grain size physical property data from SGS for robust Resource Estimate calculations and in developing mineral processing flow sheets.
Particle Size Analysis Particle size analysis is used to determine the size classification of tills, sediments or ores or to produce sized fractions for additional testing/analysis. SGS offers particle size analysis by wet screening, dry screening, a combination of both, or laser diffraction. Wet screening is preferable to dry screening for materials containing a high percentage of clays which tend to agglomerate and thus give erroneous dry screening results. Dry screen tests can be performed on a variety of materials, but the sample must be free flowing and the particles separated (i.e. unagglomerated). Often wet and dry methods are combined. Wet screening is performed to remove excessive fines then dry screening is performed to remove the oversize. Depending upon the nature of the material, dry screening, wet screening or a combination of both can be used. Laser diffraction is recommended for very fine grained samples, as it is capable of measuring particle sizes at very low limits (0.02 microns). Laser diffraction is suitable for use with both wet and dry samples.
Miscellaneous Procedures
CODE
ANALYTE CODE G_WSH_CRU G_WSH_PUL
DESCRIPTION
G_WSH G_WSH G_PRP G_RAD G_PRP G_PRP G_QRT
Barren wash after crushing stage Barren wash after pulverizing stage
PRP_COM
Compositing samples
Radiation monitoring using scintillation counter
PRP_EN PRP_EN2
Radioactive preparation environment Asbestos preparation environment Sample quarantine and handling
G_PHY15V G_PHY16V
Particle size, sieve analysis (dry or wet)
Particle size, laser diffraction
Moisture and Loss on Ignition (LOI) Many materials contain volatile components and/or moisture. SGS has a variety of tests, including moisture (H2O), loss on ignition (LOI) (at various temperatures) and thermogravimetric analysis (TGA), that provide reliable and quantitative analyses of these parameters.
MOISTURE (H 2 O) CODE
ELEMENT
LIMIT(S) ≥ 0.1% ≥ 0.01% ≥ 0.1%
DESCRIPTION
G_PHY06V G_PHY08V G_PHY17V G_PHY18V
Specific gravity - pycnometer Specific gravity - volumetric
H 2 O- H 2 O- H 2 O-
Bulk, Gravimetric determination at 105ºC Pulp, Gravimetric determination at 105ºC
G_PHY03V G_PHY04V G_PHY05V
Bulk density - immersion, waxed Bulk density - immersion, non-waxed
Penfield tube
LOSS ON IGNITION (LOI) CODE
ELEMENT
LIMIT(S)
DESCRIPTION
G_PHY01V G_PHY02V
LOI LOI
-10 - 100% -50 - 100%
Gravimetric determination at 1000ºC Multi-point TGA determinations
Note: Moisture and LOI can be determined at other temperatures. Please enquire.
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