Understanding the three Basic Types of Rock

Being a geologist is a lot like being a detective. Unlike most detectives however, being a geologist can get you a lot of strange looks. Rocks Remember. You see, I routinely talk to, and listen to, rocks. Yes, I am a geologist, and I warned you. We can be perceived as a little weird sometimes.

When you were 3 or 4 years old, someone most likely showed you a book with pictures and words in it. Although you probably recognized some of the pictures in the book, what about those words? It is impossible of course to remember what was going through your mind back then, but I think I have a little bit of an idea. Did you ever see Chinese writing? Unless you actually know the language, like me, you just stare at it with absolutely no idea of what it means. Of course, you understand the concept of words even though you can’t decipher any of them. It must be even worse for that little kid, because they don’t even understand that that scribbling next to the pictures is actually words!

And so it is with rocks. To the untrained eye, rocks are just that rocks. Ah, but to the geologist, the rocks themselves are like books, speaking in tongues unknown to the average person. The rocks tell sweeping tales about ages come and gone. They can tell you how they formed, what has happened to them since they formed, and even how old they are. Some have actually even been reincarnated and can remember their past lives. Rocks Remember

To listen to a rock, you need to learn a new language and a new vocabulary. The whole key is the concept of texture. Texture does has nothing to do with the way a rock feels, but the way that it looks. There are three different types of rocks, and each has their own unique textures.

Igneous rocks are rocks that have formed from the cooling and hardening of liquid rock. Liquid rock below the Earth’s surface (magma) cools slowly and ends up having a coarse texture, meaning that there are large mineral crystals. Check out a stone counter top in someone’s house and you will see what I mean. Liquid rock that cools on the surface (lava) does so quickly, and has a fine texture with very small crystals, and typically contains little holes or gas pockets. Rocks Remember.

Sedimentary rocks from particles of other rocks (boulders, pebbles, sand, etc) that have been compressed and cemented together and have a clastic texture. Pick up a piece of sandstone and see a former beach. Pick up a piece of conglomerate, and see a former river. Rocks Remember.

Metamorphic rocks form from other rocks by the action of heat and pressure. Think of a rock undergoing a beauty makeover or being reincarnated. The classic texture is known as foliated, and displays swirls and smeared out lines of crystals. Gneiss is a terrific example and also found on many countertops. It also tells the story of mountain building and the tremendous forces operating within the Earth. Rocks Remember.

So the next time you pick up a rock and are quick to toss it aside, stop and take the time to see what the little fellow has to tell you. It just might change your life. Rocks Remember.