Properties of Hornfels and Obsidian play an important role in determining the type of rock. Along with Hornfels vs Obsidian properties, get to know more about Hornfels Definition and Obsidian Definition. For the ease of understanding, the properties of rocks are divided into physical and thermal properties. Rocks have a variety of properties like hardness, color, specific gravity, fracture, cleavage, luster etc. Know all about physical and thermal properties of Hornfels and Obsidian.