Analysis of rocks by spectral infrared emission (8 to 25 microns), £Con

Terrestrial rock compositions can be defined by the shift in wavelength of the fundamental Si-O vibration, between 9 and 11 microns. If a sample can be polished, then normal emittahoe spectra will permit the definition of the individual minerals (and/or glass), and the rock composition can be determined with fair precision. Compositions of rock with roughened surfaces can be similarly deter-mined by normal spectral emittance or by hemispherical spectral reflectance techniques. Both methods show lower precision than that possible with polished surfaces where scattering is at a minimum. Regardless of technique used, high-silica glasses (tektites) and low-silica stoney meteorites (chondrites) show a 2.0 micron, composition-dependent displacement in wavelength of their spectral peaks. Roughness or particle size does not shift the position of such peaks, but only decreases the depth (or "spectral contrast") of their spectra. Emittance (and reflectance) processes are determined to a large extent by the "surface skin " an each crystal grain--equal-sized clear grains, frosted grains, and grains dusted with a fine powder (of the same material) will show spectra of successively diminishing contrast, each spectrum being a modification of that from the original solid (polished) material. The paper covers the results of over 330 normal emittance, reflectance, and transmittance spectra of roughened rock and mineral surfaces from 8 to 25 micron wavelengths. Field operation of flight-weight spectrome-ters is being undertaken for calibration purposes over selected geological test sites