Hardness and specific gravity are two of the major characteristics of rocks. Hardness of a rock or minneral is its resistance to scratching and may be described relative to a standard scale of 10 minerals known as the Mohs scale. F. Mohs, an Austrian mineralogist, developed this scale in 1822.
Specific gravity is the number of times heavier a gemstone of any volume is than an equal volume of water; in other words, it is the ratio of the density of the gemstone to the density of water.
The following is a table of the 10 minerals from Mohs' hardness scale:
Ruby or Sapphire
The following table shows the hardness of various common materials.
|Piece of chalk||1|
|Plaster of Paris||2|