This work presents the results of the response of fine kaolinite powder to a wide range of stress paths. Data from simple monotonic tests and those with changes of the greater principal stress direction are included. Two pieces of equipment were used, a biaxial tester and a directional shear cell. It is shown that shear strength can be described by two envelopes, one associated with the Hvorslev surface and the other with the critical state angle of friction, phi(cv). The predominant envelope is chiefly stress-path dependent. Choice of the appropriate envelope in describing shear strength is particularly important in the design of hopper exits.