nLithomargeA clay of a fine smooth texture, and very sectile.
Century Dictionary and Cyclopedia
nlithomargeOne of several imperfectly determined minerals, or mixtures of minerals, all of which are hydrous silicates of alumina, and closely related to or identical with kaolin and kaolinite. Some varieties are compact, others more or less pulverulent. The word is little used in English except as the translation of the German steinmark, literally ‘rock-marrow.’
Chambers's Twentieth Century Dictionary
nLithomargelith′o-märj a clay-like mineral substance, sometimes called Mountain marrow, soft, greasy to the touch, white, yellow, or red.