limestone
n. uncountable B2 Upper Intermediate US //ˈɫaɪmˌstoʊn// UK //lˈaɪmstəʊn// lime·stone
n. a type of white or grey rock that is often used for building. It is formed naturally over a long time from the shells and bones of tiny sea animals.
n. a hard sedimentary rock, composed mainly of calcium carbonate or dolomite, used as building material and in the making of cement.
The old church is built from local limestone.
Rainwater slowly dissolves limestone over thousands of years, which can lead to the formation of deep underground caves.
The region's unique topography is defined by its limestone bedrock, which creates a porous landscape where surface water quickly disappears into subterranean channels.
From lime + stone.
Usage
Uncountable when referring to the material; can be countable when referring to specific geological types or layers.