Alessandro Da Mommio is a mathematics and science teacher at the Istituto Salesiano S. Ambrogio, a high school in Milan. He completed his Ph.D. in geology at the University of Milan in 2015. He has maintained a passion for petrography since his undergraduate days, and for many years has built an outstanding website dedicated to the petrography of minerals and rocks. One of his images was placed second in the 2014 Photomicrography Competition. Victoria Pease is Professor of Tectonics and Magmatism at Stockholm University. Her research focuses on Arctic tectonics and she been teaching the next generation of geologists for more than twenty years. She sits on a number of international scientific committees and is Chief Editor of Precambrian Research. Victoria is co-author (with Hugh Rollinson) of the reference textbook Using Geochemical Data: To Understand Geological Processes, Second Edition (2021, Cambridge University Press).