The many measurement modes offered by the MLA implement the fundamental BSE image, and the various X-ray analyses to produce a suite of measurements designed to accommodate many different mineralogical information requirements. The measurement types and their applications are described.

Standard BSE Liberation Analysis (BSE)

This is the most basic liberation analysis method in which a series of BSE images are collected on-line and then processed off-line to produce liberation data. Mineral discrimination is based solely on BSE grey level contrast and the liberation data is generated exclusively through image analysis. BSE is employed for applications where good grey level contrast exists and a correlation between grey level peak and mineral species is established. This is the case for certain lead/zinc and copper ores and some slags.  BSE is also useful for textures or features that are finer than the resolution of X-ray analyses (i.e. 2-5 microns).

Extended BSE Liberation Analysis (XBSE)

XBSE implements area X-ray analysis to efficiently and effectively analyse ore samples containing phases with sufficient BSE contrast to ensure effective segmentation. The high resolution of BSE imaging for grain boundary definition and the speed of single X-ray mineral identification make this method ideal for a great majority of mineralogical samples.

An extension of this mode is XBSE with automated standards collection (XBSE_STD). If a spectrum from a particular phase cannot be identified using the existing library of standards, a standard for the 'unknown' phase will be collected in the usual manner and added to the library for later classification.

Ford Analysis or Grain based X-ray Mapping (GXMAP)

GXMAP employs X-ray mapping to the phases that cannot be segmented by BSE grey levels alone and the employs the faster area X-ray analysis for phases that are readily segmented. The operator selects the grains for mapping through a BSE trigger or a specific X-ray standard trigger.

GXMAP is a flexible mapping technique. It has been successfully applied to certain types of sphalerite and chalcopyrite as well as texturally complex ores, such as nickel ores containing pentlandite as fine flames in pyrrhotite. This mode was developed in collaboration with Dr. Fred Ford of Inco, Canada.

Sparse Phase Liberation Analysis (SPL)

This measurement mode searches BSE images for particles containing phases of interest using a BSE grey scale range and then performs an XBSE analysis on those particles. The off-line processing is identical to the XBSE method and generates the same mineral liberation and association data. It does not provide bulk mineralogy information, as only selected particles in the sample are analysed. The selectivity of the SPL measurement is designed to efficiently measure liberation of trace minerals in tailings and low grade feed ores, such as platinum group mineral (PGM) ores where the properties of the trace phase are the focus of the investigation.

Two specialised versions of SPL analysis are also available. SPL-Lite (SPL-LT) only measures the sparse phase of interest and its external mineral associations. This is appropriate for rock mass applications, such as drill cores, where liberation data is not relevant. SPLMAP maps the internal associations of the phase of interest once found or can be described as a GXMAP applied to a SPL.

X-ray Modal Analysis (XMOD)

XMOD is the classical point counting method in which mineral identification is determined by one X-ray analysis at each counting point. This mode uses BSE imaging to discriminate particle matter from background and then collects one X-ray spectrum from each grid point across the particle. The X-ray spectra are saved for off-line classification. This method only produces modal mineralogy information, i.e. percentages of the mineral components of the sample.

XMOD can also be implemented to produce a line scan measurement mode that produces traditional linear intercept data. X-ray spectra are taken at a step size of one pixel in the x direction and a given y displacement determines the line spacing.

Rare Phase Search (RPS)

The RPS mode searches the BSE images for phases of interest using a trigger and collects a corresponding characteristic X-ray spectrum. For each grain found, the system saves the image of the particle containing the grain, the stage location and its X-ray spectrum. The operator can subsequently move to the SEM stage location where the grain was located and manually investigate it and its surroundings further. RPS is designed to efficiently locate very fine (sub-micron) components in large particle populations, such as gold in tailings and deliver data such as grain size and associated minerals. The ability to classify off-line allows the operator to automatically eliminate other bright phases, such as galena, from the phases of interest.

Latti Analysis (SXBSE)

The Latti measurement mode adds an elemental quantification capacity to the XBSE analysis and is also known as a Super XBSE analysis. An X-ray standards trigger is employed, in a similar fashion to the GXMAP mode, to initiate a so called "long count" X-ray analysis. This X-ray collection can last 20 seconds or more and contain up to over 1,000,000 counts and is comparable with a high quality quantitative EDS measurement of the mineral concerned. These long count spectra are stored separately for subsequent analysis to obtain accurate elemental quantification for the minerals of interest, such as those with variable stoichiometry e.g. sphalerite. This mode is named after its co-developer Dewetia Latti of Rio Tinto, Australia.

Schouwstra Analysis (SPL-Dual Zoom)

Here, a standard SPL analysis is performed and when a phase of interest is detected in an image, the image capture is repeated at a higher resolution. The SPL analysis is then performed for the higher resolution particle images. This measurement mode combines the advantages of a rapid search for the phase of interest at low resolution, and that of accurate imaging at a high resolution. Schouwstra analysis is widely used for PGM minerals and is named after its co-developer Dr. Robert Schouwstra, Head of Mineralogical Research, Anglo Platinum, Republic of South Africa.