From The Collaborative International Dictionary of English v.0.48 [gcide]:
Limestone \Lime"stone'\ (l[imac]m"st[=o]n'), noun A rock consisting chiefly of calcium carbonate or carbonate of lime. It sometimes contains also magnesium carbonate, and is then called magnesian or dolomitic limestone. Crystalline limestone is called marble.
From WordNet (r) 3.0 (2006) [wn]:
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