Look for crystals or a glassy texture. If you see visible chunks of different colors—like a weird fruitcake—it’s probably intrusive. If it’s dark, dense, and has tiny holes (vesicles), you’re holding extrusive rock that once had gas bubbles trapped in lava.
Fun test: scratch a piece of unglazed porcelain tile (the bottom of a coffee mug works). If it leaves a colored streak, you might have a clue. Igneous rocks often leave telltale marks, like a signature from their fiery past.
Final weird fact: some igneous rocks, like scoria, are so lightweight and holey that pigeons actually use them as nesting material. Yes, pigeons are building homes out of solidified volcano spit. Nature, you absolute comedian.
So next time you see a chunk of granite on a countertop or a black volcanic stone in a garden, give it a little nod. It’s been through more heat than your last breakup and came out looking solid.
