Cleavage (geology)
（重定向自Slaty cleavage）
![Different ways in which a cleavage can develop in a sedimentary rock. A: original sedimentary rock; B: pencil cleavage; C: diagenetic foliation (parallel to bedding); D: slaty cleavage.](/Images/godic/202502/11/Cleavage_modes_EN.svg1855.png")
![Metamorphosed shale depicting slaty cleavage. Note the grains of mica, quartz, and ilmenite aligned with a preferred orientation.](/Images/godic/202502/11/Slaty_cleavage1855.jpg")
![A thin section depicting spaced cleavage. The cleavage domains are darker biotite grains, and the microlithons between consist of mostly muscovite and quartz. The grains in the microlithons are starting to align in a preferred orientation. A new foliation overprinted an old, showing the beginning signs of a crenulation cleavage.](/Images/godic/202502/11/Spaced_cleavage1855.jpg")
![Anticline in sandstone shale sequences with axial planar cleavage, refraction of cleavage visible on right-hand limb](/Images/godic/202502/11/Anticline_with_axial_planar_cleavage1855.JPG")
Cleavage, in structural geology and petrology, describes a type of planar rock feature that develops as a result of deformation and metamorphism. The degree of deformation and metamorphism along with rock type determines the kind of cleavage feature that develops. Generally these structures are formed in fine grained rocks composed of minerals affected by pressure solution.