ABSTRACT
Igneous rocks host a rich variety of features intrinsic to themselves, such as phenocrysts, cumulate layering, and pillow lavas. They also have features that show their relationships to the surrounding rocks, such as crosscutting contacts, chilled margins, and xenoliths. The rich variety of features, and impressive way in which they are formed, is indicated by the lavish illustrations found in many introductory geology textbooks (e.g., Marshak, 2012, p. 159).
