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Miscellaneous procedures

Miscellaneous procedures

ALS provides a wide range of methods that are useful when non-standard preparation is required. These methods include compositing samples, adding washes between samples, screening samples with multiple sieve sizes, and performing other non-routine work.

Qualidade da preparação de amostra


Compositing is the process of combining two or more sample into a single sample. This can be done by volume, core length, or by weight. This method will be performed using instructions provided to ALS.



Carryover is the contribution of elements of interest to a sample from the previous sample prepared (crushed and/or pulverised). The form in which elements of interest occur in a sample will affect the amount of carryover between samples. Smearing of samples caused by highly malleable minerals such as native copper and gold increases the likelihood of carryover significantly more than samples where metals occur within a mineral structure. Even without the presence of highly malleable native copper and gold, there can be some carryover between samples prepared using the same equipment. As part of our standard quality control procedures to minimise carryover, washes (barren material run through the equipment) are added to the crusher and pulverising bowls at the start of each new batch of samples to clean the equipment. The crusher and pulverising bowls are also cleaned with compressed air or a vacuum between every sample to remove any remaining loose material from the equipment. A request to add barren material washes between mineralised samples within a batch can be accommodated and will reduce or eliminate carryover.

Wash material

When washes are used between samples there is the option to retain the pulp produced, or have it analysed at the same time as the original samples. This can provide useful information about how much carryover is likely occur between mineralised samples and those following.


Transferring, bagging and homogenisation

ALS provides a range of methods for transferring sample to drying trays or new bags, bagging large pulps for storage, and light pulverisation for homogenisation. If any other specialised work is needed this can be performed to your specifications as needed.

Transferência, ensacamento e homogeneização


ALS preparation laboratories have a large range of screen (sieve) sizes available. These can be used individually or in sequence to characterise the grain size distribution of samples or to use multiple fractions for analysis. Please contact your preparation laboratory before submitting samples for uncommonly used screen sizes so that the lab can ensure the screens are available when samples arrive.

Sieve sizes

Sieve sizes are referred to in several ways. They can be identified by the diameter of the openings in the sieve in millimetres or microns, or as a Tyler or US number. The numbers of screens in the Tyler and US series are generally not the same so it is important to specify which numbering convention you are using, or preferably identify them by the metric opening size.




Reference Tables TN Web

Related Topics

The importance of Quality Rock Preparation

Rock preparation

The most commonly used sample preparation methods for rock samples offered by ALS are packaged together for convenience.

Soil and sediment preparation package

Soil & sediment preparation

Soils and sediments require different preparation procedures to rock samples, with low temperature drying, and screening generally utilised.