Black shales are dark, as a result of being especially rich in unoxidized carbon.
Shales that are subject to heat and pressure alter into a hard, fissile, and metamorphic material known as slate, which is often used in building construction.
Fossils, animal tracks/burrows and even raindrop impact craters are sometimes preserved on shale bedding surfaces.
The process in the rock cycle that forms shale is compaction.
Shales contain fossils and often form reservoirs of petroleum and other hydrocarbons.
Shales are typically deposited in very slow moving water and are often found in lake and lagoonal deposits, in river deltas, on floodplains and offshore of beach sands.
Shale is characterized by thin laminae breaking with an irregular curving fracture, often splintery and usually parallel to the often-indistinguishable bedding plane.
The fine particles that compose shale can remain suspended in air long after the larger and denser particles of sand have deposited out.