This Bureau of Mines report describes the geology and physical properties of core samples at the sunnyside coal mine No. 1, Sunnyside, Utah, and was written in conjunction with the single- entry program conducted at the mine. The objective of this program was to test the hypothesis that the single-entry system in the sunnyside mine, supported in the center by open cribs and divided by a fire-resistant partition, is equivalent to or better than a two- entry system. Drill cores, taken underground at 15 sites in the single-entry study area, facilitated the construction of geologic cross sections of the entries. Physical property data obtained from the drill cores was used in a three-dimensional finite element analysis program to evaluate the stability of the openings, the support requirements, and the deformation characteristics of the roof and floor material. Data on 10 physical property parameters for 5 rock types plus coal are also tabulated and discussed.