Hornfels sample approximately 1" (3cm) in size Formed at the baked contact between an intruding igneous body and the surrounding rock Perfect size for use in classroom identification labs and exercises, correlates well to Next Generation Science Standards Evidence Statements Great for students studying the effects of thermal alteration of metamorphic rocks Specimen comes in clear labeled and barcoded bag for ideal storage Hornfels forms in the narrow band between an igneous intrusion and the surrounding rock. As an intrusion propagates through the crust, the magma scorches and heats the crustal rock around it. This heat chemically alters the crust, forming a baked contact containing hornfels. This sample is good for metamorphic rock classification and identification, and is a great example of heat alteration.