Related Clues:
- Rock used for flagstones
- Site of some mammoths' demise
- Thin-layered rock
- Fossil-preserving spot
- __ oil
- Clayey rock
- Soft sedimentary rock
- Type of soft rock
- Soft rock; heals (anag.)
- Oil-rich rock
- Mineral layer involved in fracking
- Something settled long ago?
- Easily-split sedimentary rock
- Rock husband during auction
- Flagstone material