Instruments and Processing
The University of Montana X-Ray diffraction lab has two different X-Ray diffractometers:
PANalytical X’Pert PRO
The X’Pert Pro X-ray Diffractometer runs powders mounted in holders and on slides. Back-loaded powder mounts use either 16 or 27 mm diameter sample holders (show picture of sample holders) and require approximately 1 g or 2 g of sample, respectively. Up to 15 back-loaded powder mounts can be run in a batch. For smaller quantities (such as clay separates, etc), the sample is mounted on frosted glass slides.
X-rays are generated with either a copper tube with a Ni filter (run at 45 kV and 40mA) or a cobalt tube with a Fe-beta filter (run at 45 kV and 40mA), depending on the type of sample, and are detected using an X’Celerator detector. The instrument is run and data is collected using X’Pert Data Collector©.
We are currently working on establishing a mineral database with which quantitative mineralogical analyses can be performed.
Philips 3100 X-Ray Diffractometer
The Philips 3100 X-ray Diffractometer is an older unit, which is usually used for mineralogical analyses in geosciences classes. Samples are mounted on frosted glass slides.
Software and Processing
Data are collected on the X'Pert PRO with X'Pert Data Collector© software. The diffractograms are analyzed with X'Pert HighScore Plus© software, which determines background, locates peaks, and identifies the minerals and phases present. Basic Rietvelt refinement for quantification purposes can also be performed with this software (does not work for samples conatining clay minerals).
Data is collected on the Philips XRD using a Philips APD and accompanying software. These data can be analyzed with MacDiff© or X'Pert HighScore Plus©.
After the mineralogy is determined, mineral quantification of clay-rich samples is done using RockJock (http://pubs.usgs.gov/of/2003/of03-078/), a computer program developed by the USGS.