| Answer | Crossword Clue |
|---|---|
| tufa | porous rock formed as a deposit from springs or streams |
| tufas | porous limestone formed from calcium carbonate deposited by springs or the like |
| tufa | porous limestone formed from calcium carbonate deposited by springs or the like |
| tufaceous | porous limestone formed from calcium carbonate deposited by springs or the like |
| calctuff | porous limestone formed from calcium carbonate deposited by springs or the like |
| calctufa | porous limestone formed from calcium carbonate deposited by springs or the like |
