tuff

A rock composed of compacted volcanic ash varying in size from fine sand to coarse gravel.

An old spelling of tough.

Same as tuft.

A volcanic fragmental rock, varying from coarse deposits made of materials resembling fine gravel in size to those which are like the finest sand.

Same as tufa.

older and simplified spelling of tough

A light porous rock, now especially a rock composed of compacted volcanic ash varying in size from fine sand to coarse gravel.

hard volcanic rock composed of compacted volcanic ash