ELI5: Explain Like I'm 5

Grainstone

Grainstone is a type of rock that is made up of tiny grains that have been stuck together. Imagine when you're playing in the sand at the beach and you make a sandcastle. The sand you used to make the castle is made up of tiny grains, just like grainstone. But instead of using water to stick the grains together, the grains in grainstone were stuck together by something called "cement." Cement is kind of like glue for rocks. It's a substance that fills in between the tiny grains and makes them stick together so that they can become rock.

Grainstone is often found in places where there used to be a lot of water, like in the bottom of the ocean or in a riverbed. When the tiny grains of rocks and shells were carried by the water, they eventually settled down onto the bottom. Then, over a long time, the cement slowly filled in between the grains and turned them into solid rock. This rock is called grainstone because you can see all the tiny grains that make it up.

One thing that's really cool about grainstone is that it can actually tell us a lot about what the world used to be like a long time ago. Because grainstone is formed in water, it can sometimes contain fossils of animals that used to live in the water, like shells and skeletons. So when scientists find grainstone, they can study the fossils to learn about what kind of animals used to live there and even what the climate was like back then.

So, in summary, grainstone is a type of rock made up of tiny grains that have been stuck together by cement. It's often found in places where there used to be a lot of water and can contain fossils that tell us about the past.