Hardness

1
Hardness

• Hardness is a property of a mineral.
• There are different types of hardness
• Scratch Hardness
• Indentation Hardness
• Rebound Hardness
• We will be learning about scratch hardness.
• Scratch hardness refers to how easily a mineral
  can scratch other types of minerals.

Tunnel Boring Machines, like the one pictured
above, are like gigantic drills that move through
the ground. The drill uses diamond tips to grind
through the soil and rock. Why would diamond be
used instead of some sort of metal?
2
Hardness

• One of the many ways that we can measure hardness
  is using the Mohs scale.
• The Mohs scale measures scratch resistance.
• If one mineral can scratch another, it will be
  placed higher on the Mohs scale.
• For example, if a mineral is scratched by Diamond
  but not Ruby (which is just red corundum or
  sapphire), its hardness is between 9 10.
• Apatite (Hydroxyapatite) is the major component
  of tooth enamel and bone mineral.

Mohs Hardness Mineral   Chemical Formula
1 Talc Mg3Si4O10(OH)2
2 Gypsum CaSO42H2O
3 Calcite CaCO3
4 Fluorite CaF2
5 Apatite Ca5(PO4)3(OH)
6 Orthoclase Feldspar KAlSi3O8
7 Quartz SiO2
8 Topaz Al2SiO4F2
9 Corundum Al2O3
10 Diamond C