Graphite is the material in a pencil tip, and diamonds are precious jewels. They are both made of carbon. This assessment probe is to elicit students’ ideas about two seemingly different substances that are composed of the same element. It is designed to reveal how students think about substances of the same element with very different observable properties. This probe is best used with students in grades 9–12, and should be used after students have familiarity with the periodic table and have some familiarity with the concept of an isotope. The probe is provided in English and Spanish. A materials list, teacher notes, standards, assessment, and references are provided. This book selection also includes the Table of Contents, Preface, Acknowledgments, Dedication, About the Authors, Introduction, and Index.