1. A mixed earthy substance, consisting of carbonate of lime, clay, and sand, in very varivble proportions, and accordingly designated as calcareous, clayey, or sandy. See Greensand.
Marl was in high demand for farms. An example of the amount of marl mined comes from a report from 1880, from Marlboro, Monmouth County, New Jersey, which reported the following tons of marl sold during the year:
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there was plenty of chalk in the neighbourhood; and that my own ground produced excellent marle for manure
Tobias Smollett. The Expedition of Humphry Clinker (1771)
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the great oak shadowing a bare place in mid-pasture; the high bank where the ash-trees grew; the sudden slope of the old marl-pit making a red background for the burdock;