Why can two igneous rocks have the same minerals but different names?

The name of the rock can differ because of different factors. One such factor is a difference in mineral proportions. The difference in mineral proportions can be a product of the environment in which the rock was formed. Geologist can study mineral proportions to ascertain information such as the depth of formation, the temperature and pressure conditions as well as the presence of other materials.

They may have different textures.