What characteristic is unique to gneiss compared to granite?

Gneiss is recognized for its distinctive banding appearance, which is a direct result of the metamorphic processes it has undergone. During metamorphism, the minerals within granite can segregate into bands or layers due to intense heat and pressure. This differentiation of mineral types leads to the formation of alternating light and dark bands, a characteristic that is not typically found in granite. Granite, being an igneous rock, generally exhibits a more uniform texture and does not display the same layering or banding.

The other characteristics mentioned, such as porosity, silica content, and coloration, do not provide the same defining difference as banding. Gneiss may not be more porous than granite; its silica content can vary, and coloration can overlap between the two rock types. Thus, the unique banded structure of gneiss is what sets it apart from granite, making it the correct answer.