- And now, here's my friend, astronomer Amy Mainzer!

- Thanks, Jet.

Did you know that rocks can talk?

Okay, they can't really talk, but each rock has a story to tell.

Rocks are formed in different ways.

And as they get older, they can change.

Sometimes hot, squishy rock from inside the Earth gets pushed up to the surface.

When that happens, the super hot rock cools off.

And it can form all kinds of unusual shapes and textures, like this black obsidian here.

It looks like shiny glass.

Or this sparkly piece of pink quartz.

But not all rocks form this way.

Others start off as sand or dirt at the bottom of an ocean or lake.

Over a long, long, long time, the weight of the water smooshes the sand or dirt so much that it turns into rock.

That's how this rock was formed.

And look, there's a fossil fish.

That's another way that we know that this rock was formed at the bottom of what was once an ocean.

Other rocks started off as one kind of rock but then changed into something else.

Sometimes, for example, a rock can get buried deep underground.

And all that pressure can squeeze and compress it, and that can squish it into something else, like this piece of marble here.

So the next time someone asks you, "Why are you holding a rock up to your head?"

You just tell them you're listening to its story.

- Thanks, Amy.

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