Marl

n. [O. Fr. marle, merle, N. Fr. marne, W. marl, Ir. & Gael. marla, O. H. Ger. mergil, N. H. Ger., D., Dan., & Sw. mergel, Icel. mergill, L. Lat. margila, diminutive of Lat. marga, marl; whence also It. & Sp. marga, Armor. marg. Originally a Celtic word according to Pliny, 17, 7: “Quod genus terræ Galli et Britanni margam vocant.”] A mixed earthy substance, consisting of carbonate of lime, clay, and silicious sand, in very variable proportions. Marls are designated as calcareous, clayey, or sandy, according to the preponderance of one or the other main ingredient.