A natural cleft or riven face is simply achieved by splitting blocks of stone.
 Grey |
 Amazon
|
 Gris
|
 Noisette
|
Slate is a metamorphic rock, usually formed from clay sediments or
shale that has been heated and put under pressure. Slate can be black,
gray, brownish red, bluish gray, or greenish gray. It is very fine
grained and has thin, quite smooth, flat layers and easily splits into
thin flat pieces.
