shale
n. uncountablen. a type of soft rock that forms in thin layers. It is made from mud or clay that has been pressed together over a very long time.
n. a fine-grained sedimentary rock formed by the compaction of silt and clay-size mineral particles. Characterised by its fissility, meaning it splits easily into thin, flat sheets.
The hikers found pieces of dark shale along the river bank.
Geologists examined the shale layers to determine the age of the fossils trapped inside the rock.
The extraction of natural gas from deep shale formations has transformed the energy landscape, though the process remains controversial due to its significant environmental footprint.
From Middle English schale (“shell, husk; scale”), from Old English sċealu (“shell, husk, pod”), from Proto-West Germanic skalu, from Proto-Germanic skalō, from Proto-Indo-European (s)kelH- (“to split, cut”), from (s)kel- (“to split, cleave”). See also West Frisian skaal (“dish”), Dutch schaal (“shell”), schalie (“shale”), German Schale (“husk, pod”); also Lithuanian skalà (“splinter”), Old Church Slavonic скала (skala, “rock, stone”), Polish skała (“rock”), Albanian halë (“fish bone, splinter”), Sanskrit कल (kalá, “small part”); also Hittite [script needed] (iškalla, “to tear apart, slit open”), Lithuanian skélti (“to split”), Ancient Greek σκάλλω (skállō, “to hoe, harrow”). Doublet of scale. See also shell.
Usually uncountable when referring to the material; can be countable when referring to specific geological formations or types.