Measures of Hardness

Hardness is measured in many different ways.  Hardness can mean resistance to scratching, indentation, bending, breaking, abrasion, cleavage or facture.  Note that durability or toughness is independent of hardness and should not be confused.

Mohs Hardness Scale is based on scratch resistance of materials.

Brinell Hardness is based on indentation using steel ball. Diamonds are typically not measured on this scale. This test is commonly used for metals. Other indentation methods include Vicker’s, Knoop  and Rockwell Hardness Tests.

Janka Hardness is another indentation test primarily used for wood.  The test is based on the indentation of a steel ball.

The Bennett Scale is a measure of the rebound hardness (Dynamic hardness) of a material. This is done by measuring the height of the bounce (Rebound) of a diamond tipped hammer dropped from a specific height. 

Mohs Scale of Mineral Hardness

Friedrich Mohs, a German mineralogist, developed a mineral hardness scale based on the ability of a harder material to scratch another softer material.  Mohs based the scale on commonly available mineral s in 1812, and arranged them from 1 to 10, with 1 being the softest and 10 being the hardest defined by diamond as the hardest naturally occurring mineral at the time.

Mohs Scale is a relative scale and is non-linear when compared to actual hardness of the minerals.

The chart below shows the the minerals as defined by the Mohs Hardness Scale.