Clayey rock once common in building (9 letters) — Crossword Helper

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The Clue

Clayey rock once common in building (9 letter answer)

The Answer

MARLSTONE

Tags

building clayey common marlstone once rock

Notes

The answer MARLSTONE is so rare that it appears less than once every 2500 puzzles.

Definition

MARLSTONE as a noun:

1. (marlite, marlstone) = metamorphic rock with approximately the same composition as marl