Enter a clue or pattern or both:
The Clue
Porous rock (4 letter answer)
The Answer
TUFA
Tags
Notes
The answer TUFA is rarely seen, appearing only about once every 2400 puzzles.
Related Clues
Geyseral deposit
Definition
TUFA as a noun:
1. (tufa, calc-tufa) = a soft porous rock consisting of calcium carbonate deposited from springs rich in lime
2. (tuff, tufa) = hard volcanic rock composed of compacted volcanic ash