Hornfels is a non-foliated, baked rock that is formed by contact metamorphism.
The color, grain size, and mineral composition shows wide variation.
Colors can range from a light gray to a dark black. The darkest colored varieties
Granite is a light-colored igneous rock with grains large enough to be visible with the unaided eye. It forms from the slow crystallization of magma below Earth’s surface. Granite is composed mainly of quartz and feldspar with minor amounts of mica, amphiboles and other minerals. This mineral composition usually gives granite a red, pink, gray or white color with dark mineral grains visible throughout the rock.
- Pumice in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough textured volcanic glass, which may or may not contain crystals. It is typically light colored.