Far infrared absorption and laser-excited Raman spectroscopy can be easily applied to the investigation of minerals and are extremely useful for structural studies and identification purposes, especially for crystals containing heavier atoms. It is only necessary to have the crystals ground to a powder. The powder is used directly to obtain Raman spectra and as an ordinary mull for the far infrared. If a single crystal or a cluster of small crystals is available, a Raman spectrum can be obtained without any preparation at all. These points are exemplified by the spectra of As4S4 (realgar) and As2S3 (orpiment). The observed spectrum of realgar is tentatively assigned to an As4S4 molecule of the cradle type, possessing D2d symmetry. The As-S stretching and S-As-S bending regions are identified for orpiment.

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