HARDNESS, that property in bodies by which they resist abrasion from the impression of any other substance. The method pursued in constructing tables of the hardness of different substances is by observing the order in which the articles tried are capable of cutting or scratching one another. The following table, extracted from Magellan's edition of Cronstedt's Mineralogy, was taken from Quist, Bergman, and Kirwan:—
| Hard- NESS. |
Spec. GRAV. |
Hard- NESS. |
Spec. GRAV. |
||
|---|---|---|---|---|---|
| Diamond from Ormus | 20 | 3.7 | Sardonyx | 12 | 2.6 |
| Pink diamond | 19 | 3.4 | Ocidental amethyst | 11 | 2.7 |
| Blueish diamond | 19 | 3.3 | Crystal | 11 | 2.6 |
| Yellowish diamond | 19 | 3.3 | Carnelian | 11 | 2.7 |
| Cubic diamond | 18 | 3.2 | Green jasper | 11 | 2.7 |
| Ruby | 17 | 4.2 | Reddish yellow ditto | 9 | 2.6 |
| Pale ruby, from Brazil | 16 | 3.5 | Schoerl | 10 | 3.6 |
| Ruby spinell | 16 | 3.4 | Toarmaline | 10 | 3.0 |
| Deep blue sapphire | 16 | 3.8 | Quartz | 10 | 2.7 |
| Ditto paler | 17 | 3.8 | Opal | 10 | 2.6 |
| Topaz | 15 | 4.2 | Chrysolite | 10 | 3.7 |
| Whitish ditto | 14 | 3.5 | Zeolite | 8 | 2.1 |
| Bohemian ditto | 11 | 2.8 | Fluor | 7 | 3.5 |
| Emerald | 12 | 2.8 | Calcareous spar | 6 | 2.7 |
| Garnet | 12 | 4.4 | Gypsum | 5 | 2.3 |
| Agate | 12 | 2.6 | Chalk | 3 | 2.7 |
| Onyx | 12 | 2.6 |
A similar but shorter table is now generally used, in which diamond is rated at 10.