What is 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 called?

marl — 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. (Webster's 1913.)