Like other igneous rocks, the glossy glass originates from molten rock that has been spewed out from the bowels of the Earth via volcanoes. Before we get into the snowflakes, obsidian is formed ...

However, this isn’t the same kind of glass that’s used in your nice ... This molten earth origin is what classes rainbow obsidian as an igneous rock. Lava destined to become obsidian cools ...

Are they all the same? What is different about them? One of these igneous rocks formed when lava cools down very quickly, maybe with water. Can you work out which one it is? Hint: sometimes it is ...