savikivistä

Savikivi, also known as argillite, is a sedimentary rock formed from compressed clay or mud. It is denser and harder than typical shale or mudstone due to the increased pressure and diagenesis it has undergone. Savikivi is characterized by its fine grain size, often showing a dull luster. Its color can vary widely, ranging from gray and brown to red and black, depending on the presence of various minerals and organic matter.

This rock type typically forms in low-energy depositional environments, such as deep marine basins or lakebeds, where fine-grained sediments can accumulate without significant disturbance. The transformation of clay into savikivi involves the expulsion of water and the reorientation of clay minerals, leading to a more coherent and often laminated structure. While it can be easily scratched by a knife, its hardness is greater than that of unlithified mud.

Savikivi has historically been used in toolmaking, particularly for arrowheads, scrapers, and other lithic implements, due to its ability to fracture conchoidally, producing sharp edges. However, it is generally not as highly prized for this purpose as chert or obsidian. In modern times, savikivi has limited industrial applications, though it can sometimes be found as a component in certain types of building materials or as a geological curiosity. Its presence in the geological record provides insights into ancient environmental conditions and depositional processes.