During an examination of zinc ores I had occasion recently to employ methods for the identification of smithsonite, and was surprised to find how scanty and indefinite are the data of its physical properties as stated in text-books. Most of the smithsonite known occurs either compact or as very small crystals many of which are of a composite nature. In this connexion Dr. L. J. Spencer recently acquired for the British Museum some very fine crystals from the Rhodesia Broken Hill mines, and he suggested that this material would be suitable for a detailed examination. These consist of two specimens obtained in 1921 from Mr. W. E. Harris [B.M. 1921, 769] and in 1923 from Dr. O. L. Brady [B.M. 1923, 619] respectively, and are portions of the same mass. Smithsonite crystals were first described from this locality by Dr. Spencer in 1908, but these crystals were minute and showed only the forms v (201̄) and s (223̄).