Argillite

Argillite is a fine-grained sedimentary rock composed primarily of clay minerals. It forms through the compaction of clay-rich sediments, such as shale, but is less consolidated than shale. Argillite is often found in shades of gray, black, brown, red, or green, and can exhibit a variety of textures, from smooth to slightly rough. It is commonly used in carving and is known for its ability to take a high polish. The rock's formation involves the lithification of clay minerals, which are typically deposited in low-energy environments like lakes, lagoons, or deep-sea basins. Over time, the weight of overlying sediments compacts the clay, expelling water and leading to the formation of argillite. It is a relatively soft rock, making it suitable for carving and other artistic applications.