Obsidians are a type of volcanic rock that form from fast-cooling lava flows. This unique type of rock is known for its glassy appearance, dark color, and sharp edges. Synonyms for "obsidians" include volcanic glass, igneous rock, black glass, and lava glass. These terms describe the same material with slightly different angles, from the geological origin to the visual properties. Regardless of what you choose to call it, obsidian is a fascinating substance with a wide range of applications. From ancient weapons to modern scalpels, this rock has served humanity in a variety of ways throughout history.