color texture hardness origin
I gave my students this multiple choice question: Gabbro and basalt are classified as igneous rocks. Even though the names are different, they have the same chemical composition. Geologists normally use what feature for identification purposes to differentiate between these two rock types?

Only one answer is correct among these 4 choices:
- color
- texture
- hardness
- origin

Could you tell me which one is correct?

origin