Until now, we have dealt with interpretation of geologic map patterns produced by sedimentary rock layers. Of course, there are two other major rock types- Igneous and Metamorphic. We don't have to worry about being able to distinguish sedimentary rocks from their igneous or metamorphic counterparts on geologic maps by map pattern alone. Remember, the explanation tells you which rock type is represented by each color or map symbol. You will have to recognize igneous and metamorphic rock names, though. Some geologic maps even put igneous and metamorphic rocks in their own columns. Click to expand explanation.