This data release contains reflectance measurements for eight samples submitted to the USGS Organic Petrology Laboratory in Reston. Samples include two artificial rock samples made from cement with organic matter added (samples 001-002), a coal and shale sample (samples 003-004, respectively), and hydrous pyrolysis residues for samples 001-004. The hydrous pyrolysis experiments were conducted at 330°C for 72 hours at the United States Geological Survey's (USGS) Denver Federal Center. Samples were mounted into 1-inch circular briquettes in USGS-Reston according to ASTM D2797 for organic petrographic analysis. Cement plugs (samples 001-002, and pyrolysis residues 005-006) were crushed to approximately 1 mm top-size whereas rock powders (samples 003-004, and pyrolysis residues 007-008) were prepared as-received (chips and powders of varying size). Samples were mounted in a thermoplastic medium using a heat-setting hydraulic press. Examination surfaces were ground and mechanically polished to a 0.05 µm finish with a silica colloid suspension. Reflectance measurements on the coal sample and the coal pyrolysis residue followed ASTM D2798 whereas reflectance measurements on cement plugs and shales followed ASTM D7708. A Leica DM4000 microscope equipped with LED illumination and monochrome camera detection was used for reflectance analysis with the computer program DISKUS-FOSSIL by Hilgers Technisches Buero. A YAG calibration standard (0.908% Ro) from Klein and Becker was used to calibrate the microscope for all reflectance measurements.