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Understanding gemstone hardness

When considering jewellery set with a diamond or coloured gemstone, it is important to consider the stone’s hardness and how this will tie into the purpose of the piece it is set in.

What does hardness mean?

Most often the hardness of a gem is expressed as a number on the Moh’s scale. This is a relative means of measure based on what materials can leave a scratch on a particular crystal, and what can’t. Quartz, for example has a hardness of 7. It can be scratched by corundum, more commonly known as ruby or sapphire, which has a hardness of 9. Quartz can’t scratch corundum, but it can however leave a scratch on Calcite, commonly known as Alabaster, which has a hardness of 3. Diamonds are commonly known to be the hardest gemstone, and top the Moh’s scale at 10.

The majority of gemstones we use in jewellery have a hardness of 6 or more, as a hardness below this would very easily show wear from getting scratched by everyday things like keys, buttons and surfaces. It is however worth repeating that the Moh’s scale is a relative means of measure. Although corundum is diamond’s closest contender on the Moh’s scale, a diamond would measure four times harder when using a linear means of measure, so the difference is actually more noteworthy than it seems.

How does this affect me?

When purchasing a gemstone, it is important to bear in mind what it would be set in and how often this piece will be worn. The hardness of tanzanite varies from 6 to 6.5. This is a fine hardness for a pendant which is worn out of harm’s way, but becomes a point of consideration in a ring. For example, a tanzanite ring which is worn on a daily basis will more readily show wear than the same design set with sapphire as our hands are in constant contact with a multitude of hard and abrasive substances. A diamond ring worn on a daily basis will rarely show damage to its stones as most things the ring comes in contact with cannot scratch diamonds. Easy to understand then how diamonds became the go-to gem for engagement rings.

A common misconception

The technical definition of gemstone hardness, as explained by the Moh’s scale, refers to how a gem behaves when scratched by another gem or mineral. This is unrelated to the general understanding that a high hardness means a stone is indestructible. The way a diamond’s crystal structure behaves under impact is a perfect example of this. Although diamonds are basically scratch resistant, harsh impact can cause the stone to shatter or chip, so even diamond jewellery needs to be well looked after in order to be enjoyed for decades to come.

To view the widest variety of diamond and gemstone jewellery under one roof in South Africa, or to discuss your custom made jewellery dreams with a highly qualified designer, visit Mark Solomon Jewellers today.