| # | Clue | Answer As Given | Value | Round | Category | Air Date | Show |
|---|---|---|---|---|---|---|---|
| Lignite, a low-grade type of this rock, is only about 30 percent carbon | coal | $800 | J | SCIENCE & NATURE | 2004-05-24 | #4551 | |
| Brownish in color, lignite is a low-grade type of this | coal | $400 | J | NATURE | 1995-07-03 | #2511 | |
| Developed from buried peat deposits, lignite is the first stage in the formation of this fuel | coal DD | $600 | J | NATURE | 1994-02-24 | #2189 |