Here's how they differ in appearance:

Extrusive Rocks:

* Formed: From lava that cools and solidifies on the Earth's surface.

* Appearance:

* Fine-grained: Crystals are small, often too small to see without a magnifying glass. This is because the lava cools quickly.

* Porous: Often have holes (vesicles) formed by trapped gas bubbles in the lava.

* Glassy: Sometimes cooled so fast that crystals didn't have time to form, resulting in a glassy texture.

* Examples: Basalt, obsidian, pumice, rhyolite

Intrusive Rocks:

* Formed: From magma that cools and solidifies beneath the Earth's surface.

* Appearance:

* Coarse-grained: Crystals are large and easily visible because the magma cools slowly.

* Solid: Few or no holes (vesicles) because the magma is under pressure.

* Crystalline: Made up of interlocking crystals.

* Examples: Granite, gabbro, diorite

Here's a simple analogy:

Think of baking bread. If you pour batter into a pan and bake it quickly, you get a fine-grained bread with a lot of small air pockets (like an extrusive rock). If you bake the dough slowly in a Dutch oven, you get a coarse-grained bread with few air pockets (like an intrusive rock).

Key differences:

| Feature | Extrusive Rocks | Intrusive Rocks |

|----------------|---------------------|--------------------|

| Formation | Lava on surface | Magma underground |

| Cooling Rate | Fast | Slow |

| Crystal Size | Fine-grained | Coarse-grained |

| Porosity | Often porous | Typically solid |

| Texture | Glassy, Vesicular | Crystalline |