Andesite and diorite are two igneous rocks that are often confused with each other. However, there are two key physical properties that can be used to distinguish between them:

1. Color: Andesite is typically a dark gray or black color, while diorite is usually a light gray or tan color.

2. Grain size: Andesite has a fine-grained texture, while diorite has a medium-grained texture.