Why do some rocks have a few big crystals sitting in tiny ones?

What Crafty Clover says in this video

Intro

Hi there, curious minds! I'm Crafty Clover! Let's discover something amazing. Why do some rocks have a few big crystals sitting in tiny ones?

The Big Idea

Some rocks look like speckled cookies! Big crystals sit in tiny ones. How does that happen?

Porphyry

Step one: Porphyry. Some rocks, called porphyry, look like a speckled cookie. Big crystals sit in a background of tiny ones.

Slow Start

Step two: Slow Start. This happens when melted rock starts to cool slowly deep underground. That lets a few crystals grow big.

Fast Finish

Step three: Fast Finish. Then the rest of the melt rises or erupts and cools quickly, so the leftover liquid makes tiny crystals. The rock keeps a record of two cooling speeds.

A Closer Look

Let's take a closer look! It starts deep. Slow makes big. Then it rises. Fast makes tiny.

Quick Facts

Quick facts! Granite has crystals big enough to see because it cooled slowly deep underground. Like a speckled cookie. Two cooling speeds. Rocks keep records.

Think Like a Scientist

Now, think like a scientist! Press a few large beads into a lump of modeling clay. Roll tiny clay bits around them. Which part is the big crystals? Which part cooled faster? Keep beads away from little children.

Outro

Some rocks, called porphyry, have big crystals in a background of tiny ones. Melted rock first cools slowly deep underground, growing big crystals, then rises and cools fast, making tiny ones. Science is amazing! What will you discover next? Every question is a new adventure, so keep wondering and keep exploring with me! Crafty Clover can be found on Amazon Books, Google Bookstore, and Apple Books. Available for purchase or download! Bye for now!