The term 'Arrowhead Material' refers to two materials commonly used to make arrowheads: Obsidian (8 letters) and FLINT (5 letters). Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is usually black or dark in color and has been used by humans since prehistoric times for tools and weapons. FLINT, on the other hand, is a sedimentary rock composed of quartz and other minerals. It is usually gray or brown in color and has been used for centuries to make tools and weapons. Both Obsidian and FLINT are strong and durable materials, making them ideal for use in arrowheads.