Here's why:
* Nonfoliated: Hornfels lacks a layered or banded appearance, unlike foliated metamorphic rocks like schist or gneiss.
* Contact Metamorphism: This occurs when existing rocks are transformed due to heat and pressure from an intruding igneous body (like a magma chamber or dike).
* Shale or Mudstone: These are the most common source rocks for hornfels. Their original sedimentary layers are often obscured by the intense heat of the metamorphic process.
Key characteristics of hornfels:
* Fine-grained: The crystals within hornfels are too small to see with the naked eye.
* Hard and brittle: Hornfels is often quite dense and resistant to weathering.
* Variable color: Color can range from gray to black, brown, green, or even reddish depending on the original composition of the shale and the minerals present.
Let me know if you have any other questions!
