Identifying Clays in Mineral Assemblages

The accurate identification of clays in mineral assemblages can provide key indicators that mineralized systems are present (or absent). Using a field portable NIR geological spectrometer, like the oreXpress, a geologist can identify different clays in samples and note where and when alteration occurs, even in situations where visual identification is not possible. Mapping of alteration zones can provide useful information that indicates vectors to undiscovered economically viable deposits.

Using an oreXpress field spectrometer a geologist can quickly collect scans in the field at outcrops or in pits using the mineral contact probe and a handheld microcomputer, tablet, or laptop. NIR spectroscopy is fast, accurate, and non-destructive to the sample. Using EZ-ID mineral identification software a geologist can clearly seer alteration of clay minerals that often look very similar even to an experienced eye. EZ-ID matches the target spectra against three libraries (USGS, SpecMIN™ and GeoSPEC) of more than 2600 known spectra.

Where low sulfidation assemblages might include illite, montmorillonite, and sericite; high sulfidation assemblages might include kaolinite and alunite. In addition to matching the taget to the libraries with a percentage indicating confidence in the match, EZ-ID also allows a geologist to select regions of interest at various features in the spectra, for fine-tuning identification. For example, a geologist can highlight different features for different minerals in clay: kaolinite has absorption doublets near 2200 and 1400nm; smectite at 1400, 1900, and 2200nm; illite has similar features to smectite but with weaker absorption and additional features at 2340 and 2445nm.

In the core shack, the oreXpress can be used with the mineral contact probe for rapid core logging, allowing for the creation of a digital core library with all associated metadata, spectra, and notes. EZ-ID makes it fast and easy to capture alterations and identify changes in core.

Accurate identification of swelling clays, such as smectite, is also important for selecting the appropriate processing methods.

Weighing seven pounds, the oreXpress easily fits in a backpack, Two li-ion batteries provide for a full day of scanning in the field. It is ruggedly built for reliability in the field with no moving optical parts, a rugged steel-jacketed fiber optic cable (field swappable), superior cooling design, and a sealed construction to prevent contamination by dirt and dust.

The oreXpress provides a fast, non-destructive instrument for mineral identification in the field or the core shack. No sample prep is required.

EZ-ID mineral identification software allows you to match target scan against two libraries of over 2600 known mineral spectra. EZ-ID provides a match to the libraries with a degree of confidence expressed as a percentage. You can decide to fine-tune your analysis by focusing on specific features/regions within your target scan. The software will change it’s identification based-on the highlighted regions.