299 Mineralogy/Crystallography (Posters)

Wednesday, 4 November 2015
9:00 AM - 6:30 PM
Exhibit Hall

LABORATORY FAR-IR SPECTROSCOPY OF VARIOUS MINERAL GROUPS

Paper number: 299-20
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Mineral spectra in the far-IR region are highly characteristic of mineral group, crystal structure and chemical composition. This study aims at a particular application that includes mineral identification in cosmic dust populations, based on far-IR emission spectra collected by space missions such as Herschel Space Observatory Photodetector Array Camera and Spectrometer (PACS), ISO, Spitzer, SPICA, Millimetron. To provide the reference data for interpretation of spectral data returned by those or similar missions, it is important to build a database of laboratory far-IR spectra of well characterized terrestrial mineral analogs, especially at conditions relevant to those in space (e.g. at cryogenic temperatures.

In this connection, we have collected mass absorption coefficient spectra of micron-sized powders for more than 150 naturally occurring astrophysically-relevant terrestrial minerals in the wavelength range 15 - 250 µm. Low temperature (~15 K) measurements were also conducted for selected samples. The mineral samples were selected from the AMNH mineral collection, chemical and crystallographic identity of all minerals was confirmed by means of electron microprobe and grain and powder XRD. The mineral groups studied include oxides and hydroxides; a variety of sulfides; carbonates; garnets; olivines over the full compositional range from fayalite to forsterite; pyroxenes including jadeite, aegirine and the enstatite – ferrosilite and the diopside - augite – hedenbergite series; pyroxenoids; amphiboles; multiple phyllosilicates, including the serpentines, smectites, micas, kaolinites; soro- and cyclosilicates; a range of compositions across both plagioclase- and alkali- feldspars, as well as several representatives of the silica group.

Most of the minerals examined possess prominent and characteristic features in the far-IR range. For many minerals, ours are the first far-IR spectra out to 250 µm, according to literature review. Far-IR peak frequencies and mass absorption coefficient values are tabulated.