Hardness
Identifying Mineral Characteristics

The determination of the hardness of a mineral can be an important step toward its identification. The hardness of a mineral is defined as the resistance it offers to being scratched. Hardness is usually expressed as a value ranging from 1 to 10, with 1 being the softest mineral and 10 being the hardest. The scale that expresses hardness in this way is known as the Mohs' Scale of Hardness.
Mohs Scale of Mineral Hardness


Hardness
Mineral
Uses
1
Talc
  Talcum power
2
Gypsum
  Plaster of Paris. Gypsum is formed when seawater evaporates from the Earth's surface. 
3
Calcite
  Limestone and most shells contain calcite.
4
Fluorite
  Fluorine in fluorite prevents tooth decay.
5
Apatite
  When you are hungary you have a big "appetite".
6
Feldspar
 Im German, "feld" means "field".
7
Quartz
  
8
Topaz
  The November birthstone. Emerald and aquamarine are varieties of beryl with a hardness of 8.
9
Corundum
  Sapphire and ruby  ar varieties of corundum. Twice as hard as topaz.
10
Diamond
  Used in jewelry and cutting tools. Four times as hard a corundum.

An additional scale, the Field Scale of Hardness, relates common objects to Mohs' Scale.


Field Scale of Hardness
Fingernail 2.5
Copper Coin 3
Iron Nail 5
Glass 5.5
Steel File 6.5

 
Copper Coin Scratches Mineral
Mineral is softer than 3 on the Mohs Scale of Mineral Hardness

 
 
Copper Coin Does Not Scratch Mineral
Mineral is harder than 3 on the Mohs Scale of Mineral Hardness

 
 
 
Iron Nail Scratches Mineral
Mineral is softer than 5 on the Mohs Scale of Mineral Hardness

 
 
 
Iron Nail Does Not Scratch Mineral
Mineral is harder than 5 on the Mohs Scale of Mineral Hardness

 

One of the most important hardness tests is whether a mineral will scratch glass.

Mineral Scratches Glass
Mineral is harder than 5.5 on the Mohs' Scale of Mineral Hardness

 
 
 
Mineral Does Not Scratch Glass
Mineral is softer than 5.5 on the Mohs' Scale of Mineral Hardness

Follow these steps to Identify Your Minerals:
Getting Started
Color
Hardness
Streak
Luster
Cleavage
Rock Samples

 
St. Joseph's Intermediate GrassRoots Project 2001-02