| 2026-06-02 | Rock that's fracked to release oil |
| 2026-05-02 | Soft rock |
| 2025-05-23 | Cement ingredient |
| 2025-02-17 | Layered rock |
| 2024-05-11 | Burgess ___ (rock bed noted for its fossils) |
| 2024-03-07 | Layered rock |
| 2023-11-08 | Flaky rock |
| 2023-07-14 | Fracking target |
| 2021-06-13 | One source of oil |
| 2021-03-31 | Thin-layered sedimentary rock |
| 2020-07-24 | Rock in which fossils can be found |
| 2019-11-01 | Some mudrock |
| 2018-12-29 | Oil source |
| 2017-08-28 | Oil-producing rock |
| 2017-06-23 | Fracking target |
| 2017-01-10 | *Sedimentary rock |
| 2016-12-24 | Something fracked in fracking |
| 2016-11-02 | Fuel-yielding rock |
| 2016-03-08 | Fracking material |
| 2014-12-04 | Something settled long ago? |
| 2014-12-01 | Mineral layer involved in fracking |
| 2013-10-06 | Rock used for flagstones |
| 2012-10-15 | Oil-producing rock |
| 2009-06-27 | Oil source |
| 2009-04-19 | Fossil source |
| 2009-02-20 | Slate, originally |
| 2008-11-30 | Fossil-yielding rock |
| 2006-03-03 | Shelf material |
| 2004-11-12 | Fossil medium |
| 2003-10-01 | Oil source |
| 2003-09-06 | Brick ingredient |
| 2003-03-28 | Oil source |
| 2003-03-09 | Petroleum source |
| 2002-08-02 | Mudstone |
| 2001-12-05 | Oil source |
| 2000-08-10 | Rock that may hold fossils |
| 1999-10-01 | Synfuel source |
| 1998-10-14 | Oil source |
| 1997-10-25 | Kind of oil |
| 1996-02-19 | Laminated rock |
| 1995-04-10 | Laminated rock |
| 1994-01-16 | Oil source |
| 1993-11-25 | Easily split rock |