The physical properties of rocks may be used for three purposes. First and most valid, they may be used for comparisons and classifications based on their behavior under various types of loads. Secondly, an effort may be made to correlate the elastic properties for engineering and geophysical purposes. Finally, a knowledge of these properties is essential in connection with the design of rock structures. This paper summarizes the results of several years' work at McGill University and describe the testing procedures that are used. A summary table of the physical properties of several rocks from various Canadian mines is included, and our plans for future additions to the table are discussed. A few examples have been chosen to demonstrate their use when applied to actual problems.