n. A soft, earthy, dark-coloured rock or clay derived from the alteration of basalt.
the GNU version of the Collaborative International Dictionary of English
n. A soft, earthy, dark-colored rock or clay derived from the alteration of basalt.
The Century Dictionary and Cyclopedia
n. A soft homogeneous clay arising from the decomposition of some form of volcanic or eruptive rock. It is of a greenish or brownish color. Compare graywacke.
Word Usage
"The basis of these lower lavas is rather wacke than basalt; when it is spongy, it resembles the amygdaloids* of Frankfort-on-the-Main."