Earth is made of a variety of solids, liquids, and gases. Geologists call the substances earth materials. Each earth material is a nonliving substance that makes up Earth’s interior, surface, or atmosphere. Geologists who study the earth focus their work on the solid materials called rocks. Geologists have discovered many kinds of rock that form Earth’s crust.
Once of the challenges a geologist faces is to determine the ingredients in different kinds of rocks. Many earth materials combine to make rocks, just as you combine the ingredients in a kitchen to make chocolate-chip cookie or raisin bread. Once a geologist knows a rock’s ingredients, he or she can generate ideas about the origins of the rock.
In the field, geologists make careful observations and keep detailed records of the rock’s physical appearance. Color, size, shape, texture and mass are some of the properties the geologist records.
Real rocks are very difficult to take apart. The ROSS program invented softer, more manageable mock rocks to provide a good simulation for the procedures used by geologists.
Some important rock characteristics:
Color: Although often used to identify specimens, color may not always be an accurate property to use for identification.
Hardness: A measure of how easily a rock or mineral can be scratched.
Luster: Characterized by the way light is reflected from the surface of the specimen (shiny to dull.)
Streak: Minerals leave a characteristic streak when rubbed across unglazed porcelain, revealing the color of the power of the mineral.
Today, we dissected rocks. The kids had so much fun!
Here is what some of them had to say: