Petrology and Geochemistry Lab

Rocks and their chemical constituents

The petrology and geochemistry lab houses several key tools and support equipment for the evaluation of rocks and minerals. The lab has a high-end polarizing light microscope and imaging system, as well as binocular and digital microscopes for evaluating the optical properties and surface features of rock fragments, thin sections, and mineral grains. Support equipment includes cleaning, heating, and polishing equipment.

X-ray Powder Diffraction

The lab houses the KSG's Rigaku Miniflex 600 X-ray diffractometer (XRD). This is a bench-top sized diffractometer that permits characterization of mineral powders. The Miniflex diffracts X-rays from a Cu tube through a powder sample; these are refined by a quartz monochronometer and collected with a scintillation detector as a function of incident-diffraction angle. The PDXL2 software is coupled with the ICPDD PDF-2 database to resolve the identity of powdered samples of single-phase materials (rocks and other solid media containing one mineral). Additionally, the software can determine the mineral and amorphous phase fractions in polymineralic materials, such as most rocks.

The MSU XRD has been used for identifying unknown mineral samples, but its chief use is resolving mineral concentrations and phase identification in granites and limestones. Current work focuses on improving Rietveld refinement techniques on assessing mafic silicate minerals and assessing weathering in granites.

Laser Induced Breakdown Spectrometer

The lab also contains a Laser Induced Breakdown Spectrometer (LIBS) for micro-sample analysis of earth materials. LIBS uses a powerful focused ultraviolet laser beam to ablate a small volume of a sample into a plasma. The light emitted from the plasma is collected and spread out (refracted). The elements in the plasma (from the sample and surrounding air) emit intense light at characteristic wavelengths. When the light is refracted, these characteristic wavelengths produce higher intensity peaks. These reveal the composition of the ablated material.

The MSU LIBS has been employed in characterizing feldspar and amphibole minerals from southern Oklahoma, gypsum from west Texas, and a number of other mineral and synthetic crystalline samples. It is extensively used in our  Mineralogy, Petrology, and Geochemistry classes. Current work focuses on data processing techniques useful to quantitative analysis.