In this work we introduce a content Ontology Design Pattern (ODP) to model and reason about material transformations, a concept that occurs in many different domains ranging from computational chemistry, biology, and industrial ecology to architecture. We model the relationships between inputs, outputs, and catalysts in the transformation process as well as the spatial and temporal constraints necessary for a transformation to occur. Both a graphical illustration and a formal axiomatization are provided, and the commonalities and differences to similar ontologies and patterns are discussed. Usage of the pattern is illustrated by applying it to an intuitive and familiar example and by discussing how the pattern is able to address a set of competency questions. Additionally, we present a detailed use case from the domain of sustainable construction that leverages the material transformation pattern in combination with the already-existing semantic trajectory ontology design pattern.