This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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adj. Composed of, containing, or characteristic of calcium carbonate, calcium, or limestone; chalky.

adj. Resembling or containing calcium carbonate or limestone; chalky.

adj. Partaking of the nature of calcite or calcium carbonate; consisting of, or containing, calcium carbonate or carbonate of lime.

Partaking of the nature of lime; having the qualities of lime; containing lime; chalky: as, calcareous earth or stone.

adj. composed of or containing or resembling calcium carbonate or calcite or chalk

"Another concern is what the acid might do to the specific algae called calcareous coralline algae that holds the coral reefs together and act as a substrate or base upon which corals can grow."

calcareous tufa    calcareous algæ    calcareous spar    calcareous sponges    calcareous sacs   

siliceous    argillaceous    porous    stratified    alluvial    ferruginous    friable    clayey    volcanic    granular