| 2023-09-03 | Eponymous mineralogist Friedrich |
| 2023-07-10 | ___ scale (measure of hardness) |
| 2022-11-02 | Friedrich who created a scale of hardness |
| 2020-09-03 | Mineralogical eponym |
| 2020-08-10 | ___ scale (rater of mineral hardness) |
| 2019-01-15 | Eponymous scale inventor |
| 2017-08-18 | ___ scale |
| 2016-10-04 | ___ scale (measure of hardness) |
| 2015-09-18 | Inventor of a mineral hardness scale |
| 2014-10-03 | ___ scale |
| 2014-09-30 | Mineralogist for whom a scale is named |
| 2012-12-10 | Kind of scale of mineral hardness |
| 2011-02-22 | ___ scale |
| 2010-04-11 | Hardness scale inventor |
| 2010-03-04 | Eponymous scale developer |
| 2009-12-27 | ___ scale |
| 2009-09-23 | ___ scale |
| 2006-10-08 | ___ scale |
| 2006-04-20 | Mineralogist Friedrich |
| 2004-07-22 | Mineral hardness scale inventor |
| 2004-03-09 | Scale of mineral hardness |
| 2003-09-20 | Eponymous German mineralogist |
| 2003-08-13 | Kind of scale |
| 2002-02-07 | ___ scale |
| 2001-04-06 | Kind of scale |
| 1999-03-13 | ___ scale |
| 1995-05-03 | _____ scale (hardness measure) |