Mohs' Scale of hardness is basically a scratch test,
"The resistance of a mineral when scratched with a pointed testing object".
The scale is not even, meaning that something with a Mohs' hardness
of 5 is not a set amount harder or softer than a 4 or 6.
| 1 | Talc | Breaks apart easily in the fingers when squeezed |
| 2 | Gypsum, Sulphur | Can be scratched by a fingernail |
| 3 | Calcite, Amber | Can be scratched by a penny |
| 4 | Fluorite, Turquoise | Can be easily scratched with a knife point |
| 5 | Apatite, Obsidian | Can be scratched with a knife point |
| 6 | Pyrite, Orthoclase | Can be scratched with a steel file |
| 7 | Quartz, Tiger's Eye | Can scratch glass |
| 8 | Topaz, Aquamarine | Slightly harder than Quartz |
| 9 | Ruby, Sapphire | 2 times harder than Topaz or other number 8's |
| 10 | Diamond | 4 times harder than Ruby or other number 9's |