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Definitions of Mechanical Properties of Natural Stone

What is Specific Gravity

The Specific Gravity is referring to the weight of a material and is measured in grams per cubic centimetre. Assuming a natural stone has a Specific Gravity of 2.7, it means that its weight is 2.7 grams per cubic centimetre, or 2700 kg per cubic metre. The Specific Gravity of natural stones is usually around 2.5 to 3.0, depending on the density and kind of the containing material.

What is Bending Strength or Flexural Strength?

The Bending Strength (or Flexural Strength) measures the force a material can resist when bended. It is measured in N mm-2 and shows the forces applied to a material in the moment of failure.

What is the Young’s Modulus or Modulus of Elasticity?

The Young's Modulus (or Modulus of Elasticity) describes the limit for small strains of the rate of change of stress with strain a material is able to support. Many natural stones have a Modulus of Elasticity of around 50 Gpa (which translates to 50.000 N mm-2, depending on the stone), with pure Quartz reaching a Young’s Modulus of 71.7 GPa.

What is Mohs Hardness?

The Mohs Hardness describes the scratch resistance of the surface of a natural stone (or indeed any other mineral). The Mohs Scale is not defined by forces or applied pressure, but rather by definitions. It goes from 1 (softest material) to 10 (hardest material). The surface hardness of Quartz, for example, is defined as the value 7 in the Mohs Scale. Granite usually has a value of around 6.5 on the Mohs Hardness scale, which means that is can be scratched using pure Quartz. The values and their corresponding minerals are: Talc (1); Gypsum (2); Calcite (3); Fluorite (4); Apatite (5); Orthoclase Feldspar (6); Quartz (7); Topaz (8); Corundum(9); Diamond (10).

The background stone is Verde Tunas from Brazil.
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