Abstract: A method of treating and grading contaminated particulate material includes i. physically breaking up the particulate material to separate the particles thereof; ii. rinsing and grading the particulate material to separate the particulate material into an oversize fraction and an undersize fraction; iii. washing and grading the oversize fraction to produce one or more treated aggregate products; iv. passing the undersize fraction through a high shear washing process to separate contaminants therefrom; v. fluidising and cleaning the undersize fraction in a classification tank to produce one or more treated sand products at an underflow thereof by passing clean water upwardly into the classification tank. Optionally, waste water resulting from stages (ii), (iii) and (iv) is treated to form process water, a portion of which is used in stage (ii), a portion of the process water undergoing one or more further treatment processes to produce clean water used in stage (v).