The Department of Mineral Sciences' role is not only to take care and grow the Gem & Mineral collection, but also to use the collection as a research tool, and to be active in the Science world, by publishing and giving presentations at local, national, and international conferences. Dr. Aaron Celestian's specialty is determining chemical evolution of minerals on short time-scales, and Dr. Tony Kampf's specialty is mineralogy and crystallography, discovering and describing new minerals. To know more about Dr. Celestian click here, or Dr. Kampf click here.
The Mineral Sciences Laboratory is on public display as of November 2017. All experimental stations, collections, and equipment are on view and scientific content is communicated to the visitor by signage, gallery interpreter engagement, video, and social media to our more than 800,000 visitors a year.
The Mineral Sciences Department is outfitted with a Horiba ExploRa+ dispersive Raman microscope. Two lasers can be selected, a 532 nm and a 785 nm, with automated calibration for each laser. Typical Raman spectra for the 532 nm laser can be collected from 70 cm-1 to 4500 cm-1, while the 785 nm laser spectral range is nominally from 40 cm-1 through 2500 cm-1. Slits can be used to obtain better spectral resolution from a selection of 50, 100, 200um, and the microscopic can be used in confocal mode by selecting a pinhole, 100, 200, and 500 um. Laser power at the sample is adjustable, with a maximum of 15.2 mW at the sample. Diffraction grating options are 600 gr/mm, 1200 gr/mm, 1800 gr/mm, and 2400 gr/mm, where the 1800 gr/mm is most commonly used. A 10x (0.1 N.A.) and 100x (0.9 N.A.) objectives are available. An automated XYZ stage controls sample positioning and mapping procedures. Calibrations are performed daily and ambient room temperature is recorded every 5 minutes. Temperature changes can affect the measured positions of the Raman bands.
The micro-XRF analyzer (Horiba XGT-7200) is used for single point, multi-point, hyperspectral mapping analysis, and transmitted X-ray imaging. The spatial resolution of the instrument is adjustable by means of computer-controlled switching between the 50 micron and 1.2 mm X-ray guide tube. Dual vacuum modes (full and partial) allow for solid and liquid analysis. For liquid analysis, then a vacuum is applied to the detector and X-ray optics while the sample chamber is maintained at ambient pressure. The elemental range is from Na to U, and Rh target is used with a maximum tube power at 50 kV and 1 mA.
The Rigaku R-Axis II is used to determine the atomic structure of crystals. Crystals typically need to be less than 300 microns on edge, and larger than 5 microns on edge. The R-Axis II also can do powder diffraction of single crystals or aggregates of crystals that would normally be too small for dedicated powder diffraction instruments.