Remote Raman spectroscopy of nature rocks

We report the remote Raman spectra of natural igneous, metamorphic, and sedimentary rock samples at a standoff distance of 5 m. High-quality remote Raman spectra of unprepared rocks are necessary for accurate and realistic analysis of future Raman measurements on planetary surfaces such as Mars. Our results display the ability of a portable compact remote Raman system (CRRS) to effectively detect and isolate various light- and dark-colored mineral phases in natural rocks. The CRRS easily detected plagioclase and potassium feldspar end members, quartz, and calcite in rocks with high fluorescence backgrounds. Intermediate feldspars and quartz, when found in rocks with complex mineralogies, exhibited band shifts and broadening in the 504-510 cm(-1) and 600-1200 cm(-1) regions. A good approximation of intermediate plagioclase feldspars was possible by using overall Raman spectral shape and assigning other minor Raman peaks in addition to the 504-510 cm(-1) peaks. Detection of olivine and pyroxene in maficrocks allowed for compositional characterization. (C) 2019 Optical Society of America