Moving from micron-size systems (single crystals) to planetary-size bodies, the articles in this issue will explore the enormous range of temporal and physical scales over which heavy stable isotopes have provided paradigm-shifting insights into the evolution of our planet and solar system. Steady advances in mass spectrometry have allowed isotopic inquiries to move from the so-called “traditional” systems (i.e., H, C, N, O, and S) to heavier “nontraditional” systems (e.g., Fe, Mo, Ti, Zr, U) whose diverse geochemical characteristics are providing novel and complementary insights. Since their discovery in 1913, stable isotopes have become formidable tracers of physicochemical processes at all scales. Tissot(California Institute of Technology, USA) and Mauricio Ibañez-Mejia (University of Arizona, USA) V17n6 Heavy Stable Isotopes: From Crystals To Planets The Distinctive Mineralogy of Carbonatites.Formation of Rare Earth Deposits in Carbonatites.Carbonatitic Melts and Their Role in Diamond Formation in the Deep Earth.Evolution of Carbonatite Magmas in the Upper Mantle and Crust.Carbonatites: Contrasting, Complex, and Controversial.This issue explores the current models for how carbonatites form and evolve in the mantle or crust, the temporal and tectonic controls on their formation, why they are so enriched in rare earth elements, and what are their economically significant minerals. The popularity of high-tech devices-smart phones, electric motors for zero-emission vehicles, wind turbines for renewable energy-has led to a renewed focus on these enigmatic carbonatite magmas, because to make these devices requires rare earth elements and the majority of the world’s rare earth elements are associated with carbonatites. They are composed dominantly of the Ca, Mg, and Fe carbonates, along with many other minor and trace components. Carbonatites are rare, but important, igneous rocks in the Earth’s crust.