This is a revised and updated edition of the highly successful first and second editions. In the intervening period the procedures used in the description of soils and rocks have continued to develop and evolve and this new edition incorporates changes in the international standards EN ISO 14688 and 14689 and those resulting in the national standard, BS 5930:2015 and the 2020 amendment thereof. Close comparison is also made with US practice in description (ASTM D2488) and classification (ASTM D2487). Significant changes in rock description are included – the reintroduction of the Approaches 1 to 5 for rock weathering; Approach 1 for description and Approaches 2 to 5 (Rock Weathering Working Party) for classification when appropriate and helpful. Also covered is the reintroduction of the 12.5 MPa boundary and the term moderately weak in rock strength description: a significant boundary in design in rock. The book continues to provide invaluable practical guidance in carrying out engineering geological logging of soil and rock samples and exposures in the field. The systematic and codified approach is laid out in detail to ensure the defined descriptors are used in a consistent format, rendering mistakes less likely and the necessary communication from field to design more successful. The procedures, techniques and tips within this book continue to serve and guide young practitioners learning their craft, but also their seniors and mentors, including responsible experts who sign off the logs and report on behalf of their company. More than ever, the need to be aware of current practices in order in order to avoid costly mistakes is paramount.