Hornfels, a metamorphic rock, is characterized by:

Hornfels, a metamorphic rock, is characterized by:

• A. Layered foliation
• B. Uniform texture with no banding
• C. Glassy appearance
• D. Alternating bands of light and dark crystals

Answer: (D)

Hornfels forms when rocks are baked by a nearby magma body, and the pressure is not directional. That means minerals recrystallize in place without creating aligned layers or foliations. The result is a dense, fine-grained rock with a uniform texture that appears smooth and nonfoliated across the sample. In contrast, alternating bands of light and dark crystals indicate mineral segregation under directional stress, a feature common to rocks like gneiss, not hornfels. A glassy appearance would point to obsidian or other volcanic glasses, not hornfels. So the key idea is that hornfels has a nonfoliated, uniform texture due to high heat but relatively low directional pressure.

Hornfels forms when rocks are baked by a nearby magma body, and the pressure is not directional. That means minerals recrystallize in place without creating aligned layers or foliations. The result is a dense, fine-grained rock with a uniform texture that appears smooth and nonfoliated across the sample. In contrast, alternating bands of light and dark crystals indicate mineral segregation under directional stress, a feature common to rocks like gneiss, not hornfels. A glassy appearance would point to obsidian or other volcanic glasses, not hornfels. So the key idea is that hornfels has a nonfoliated, uniform texture due to high heat but relatively low directional pressure.