They are everywhere. We live on them, build with them, create art with them. What are we talking about? Rocks! Rocks are everywhere and they are important to our lives. They tell the story of the history of the Earth. That is why rock scientists, called geologists, study rocks. I bet that you have a rock collection, or can find rocks just outside in your yard or a nearby park. What secrets about Earth’s history do your rocks tell you?
To discover a rock’s secret, do what a geologist would do. Be very quiet, hold it to your ear and listen. What did it tell you? Did it tell you how it was formed? Nothing? Well, of course not! Rocks are nonliving things. Rocks are made in nature. It means they formed without the help of you or me. Nature has been forming rocks like those found in the Grand Canyon for millions of years. It’s amazing!
Rocks can be made of minerals, volcanic glass, or changed matter from plants. Most rocks are made of one or more minerals. A mineral is a natural material that forms from nonliving matter. Minerals are the building blocks from which rocks are made. They might not be talking, but we can still learn from them. To learn their secrets we have to use our eyes and our hands to study them.
We can start our study by sorting them by certain characteristics. These characteristics can be size, shape, texture or color. Can you sort your rocks by color? Rocks can be a bright color such as red or orange. They can be dull colors such as brown and gray. Minerals give rocks their color. A mineral crystal gives rocks their sparkle. Crystals are hard, clear matter that have points and flat sides and can be large or small. Are there any crystals in your rocks? Do your rocks have the same color when they are wet as when they are dry?
Have you noticed that rocks have different textures? Texture describes how they feel. Can you sort your rocks into smooth, bumpy, or gritty rocks? Rocks get their texture by how they cooled. If your rock has “holes” like Swiss cheese, then your rock has gas bubbles. It might have been blown out of a volcano. Do you see any imprints of leaves, shells, insects, or other items in the rocks? This means that you have a fossil in your rock. How do you think the fossil formed in your rock?
You can go outside to find more rocks to add to your collection. Pick them up. Turn them over. Look at all of their sides. What size and shape are they? Why are rocks different sizes? Do rocks stay the same? Do they change? These are the types of questions you need to ask and research to learn your rocks’ secrets.