Diamonds Are Forever

"A Diamond is Forever" carries a few different meanings. It refers to a diamond's timeless appleal and its clear icy beauty. It also refers to diamond's durability.

Durability is a gemstone's ability to withstand wear, heat, and chemicals. It varies from gem to gem, depending on chemical composition and structure. One side result of the diamond formation process is incredible durability.

In the industry, durability consists of three properties:

• Hardness
• Toughness
• Stability

Many people think hardness and toughness are the same thing however, in gemology, they have very specific and separate meanings.

Hardness means resistance to scratching:

This is how a stone's surface responds to contact with a sharp point, to the edge of abrasive powders, or to rubbing against the surface of another gem.

The Mohs Scale (pronounced MOZE) rates the hardness of gems and minerals. The scale originated in 1822 when Friedrich Mohs chose ten minerals and assigned numbers to them, based on the relative ease or difficulty with which one could be scratched by another. The resulting scale is now an industry standard:

Diamond	10
Corundum	9
Topaz	8
Quartz	7
Orthoclase Feldspar	6
Apatite	5
Fluorite	4
Calcite	3
Gypsum	2
Talc	1

According to the Mohs scale, quartz can scratch any mineral with a hardness of 7 or less. Corundum (which includes rubies and sapphires) can scratch any mineral with a hardness of 9 or less. Only a diamond can scratch a diamond.

Toughness means resistance to breaking, chipping or cracking:

This is how well a stone can survive impact from a fall or a blow.

Any stone, including a diamond, will fracture if it's hit hard enough in the right place. The way diamonds form affects their physical and optical qualities. When the atoms come together under extreme temperature and pressure conditions, they bond to each other more tightly in some directions than they do in others.

A cutter can cleave a diamond by hitting it sharply in the cleavage direction. But even after cutting, a hard blow can still cleave or fracture a diamond. This can happen during the setting process, or even when it's being worn.

Sometimes the toughness of a diamond is related to its cut features and shape. For example, a diamond with an extremely thin girdle is especially vulnerable to damage. Also, some shapes are more prone to breakage than others. Pears and marquises, for example, have points that are vulnerable to damage if they're not covered by prongs.

Summary:

Hardness -	Resistance to scratching.
Toughness -	Resistance to breaking, chipping or cracking.