In this LOP Presentation, Professor Evert Hoek is providing insights into the use of rock masses as engineering materials with an emphasis on large open-pit mine slopes. The presentation is based on Prof Hoek’s recent public talk at a symposium in Brisbane in December 2018 for the celebration of the 80th birthday and the retirement of Professor Ted brown. The paper presented in 2018 was entitled “The Hoek-Brown Criterion and GSI 2018 Edition”, and is published in the journal of Rock Mechanics and Geotechnical Engineering. It is noted that the Brisbane presentation was for a general audience, and Prof Hoek has made several significant changes in this LOP presentation in order to emphasize some of the issues related to the design of open-pit mine slopes. The overall message has not changed, but the examples are different from those of the original paper.