Hardness Rock Note 1 Talc marks paper 2 Gypsum fingernail (just) 3 Calcite crystallized calcium 4 Flourspar copper coin 5 Apatite 6 Felspar Knife 7 Quartz 8 Topaz 9 Corundum Carborundum is 9+ 10 Diamond scratch anything!
(Note; [is] Rock [of]; Hardness)
Note
[is] Rock [of]
Hardness