| # | Clue | Answer As Given | Value | Round | Category | Air Date | Show |
|---|---|---|---|---|---|---|---|
| If a mineral is scratched by topaz but not quartz, its hardness lies between 7 & 8 on this scale | the Mohs scale | $1,600 | DJ | EARTH SCIENCE | 2014-12-23 | #6967 | |
| The hardness of a mineral is often measured on this scale named for a German mineralogist | the Mohs scale | $400 | J | EARTH SCIENCE | 1991-04-10 | #1533 |