Ore Grade Analysis, Mineral Concentrates and Industrial Minerals
We continue to emphasise the importance of classifying samples according to their expected concentration ranges. To accommodate samples with significant mineralisation, ALS has a full range of ore grade assay procedures. Ore grade samples by definition are of economic significance and as such, ALS guarantees a high level of accuracy and precision.
This issue is discussed further in the section entitled Accuracy and Precision in the Quality Assurance section.
Our group has performed umpire analysis for many years in the field of Mineral Concentrates. We use internationally recognised ISO methods for these analyses, which are performed in separate facilities to minimise cross contamination of lower grade samples.
ALS is a world leader in the commercial analysis of industrial minerals; commodities that are often passed over in the hunt for more attractive base metal deposits. We have proven expertise in this area, and have a dedicated laboratory for analysis of materials from this sector.
Ore Grade Analysis
For simple characterisation of ores, recommended procedures include; the aqua
regia digestion (OG26) primarily for lead/silver/zinc rich ores and; four acid
digestion method (OG62) for copper and zinc ores with low lead, and silver and
nickel laterite ores. Samples expected to contain significant amounts of
sulphides of copper; nickel and/or cobalt are fused with sodium peroxide and
then leached with dilute hydrochloric acid using procedure ICP-81.
Metallurgical Mass Balance Procedures – Carbon and Sulphur
The metallurgical processing of reduced materials requires the determination of
carbon and sulphur, and usually their oxide forms. Total carbon is determined by
an ignition process, while carbon dioxide is measured volumetrically. To
determine total organic carbon, a sample is leached with dilute hydrochloric
acid to destroy carbonate and then the sample is ignited similarly. Inorganic
carbon (i.e. carbonate) is determined by the amount of carbon dioxide generated
when a subsample is treated with dilute hydrochloric acid. Graphite, if present,
will report with the total organic carbon. Total sulphur is determined by a
similar ignition process, but in this case the sulphur dioxide produced is
measured using infrared spectroscopy. Samples for sulphate sulphur are leached
with dilute hydrochloric acid, then filtered and the dissolved sulphate is
measured gravimetrically by precipitation of barium sulphate. Samples for
sulphide sulphur are digested with nitric acid and bromine to convert sulphide
to sulphate. As only a portion of sulphate dissolves in this process,
hydrochloric acid is then added to complete the sulphate digestion. The combined
sulphate is then determined gravimetrically by precipitation as barium sulphate.
The sulphide sulphur is the difference between the %S of this test and the %S
found by sulphate sulphur; procedure
Mineral Concentrates
We maintain separate laboratory facilities for the testing of mineral
concentrates due to the potential contamination risk. It is in these facilities
that we carry out control and umpire assays for all non-precious metals.
Iron Ore, Bauxite and Bulk Industrial Minerals
Iron ore and bulk minerals, such as quartz, limestone or bauxite, play in an
important role in a wide range of industrial applications. Exploration
geologists searching for base metal deposits may overlook the commercial
importance of evaluating the bulk material content associated with the base
metal of interest. ALS offers analytical expertise in the assessment of bulk
minerals from the exploration stage to deposit evaluation and mine production
and finally, analysing product shipment samples.