Understanding the resistance of precious stones using the Mohs scale

What is the Mohs scale?

Created in 1812 by mineralogist Friedrich Mohs, this scale ranks minerals according to their ability to scratch another material. It ranges from 1 (talc, extremely brittle) to 10 (diamond, the hardest stone known). In practical terms, a stone graded 7 will be able to scratch a stone graded 6, but will itself be scratched by a higher graded stone.

The impact of hardness on jewellery

In jewellery, the hardness of a stone plays a crucial role in its durability. For example, a diamond (10 on the scale) is ideal for an engagement ring, as it resists scratches and everyday knocks. On the other hand, a stone like opal (around 5-6) requires more attention and care to avoid scratches.

Here are some examples of stones commonly used in jewellery and their hardness on the Mohs scale:

• Diamond 10 (very resistant, ideal for everyday wear)

• Sapphire and ruby 9 (excellent resistance, perfect for rings and bracelets)

• Topaz 8 (solid but may chip on impact)

• Quartz : 7 (fairly resistant but sensitive to shocks)

• Opal and turquoise : 5-6 (fragile, handle with care)

How do you choose?

If you are looking for a piece of jewellery to wear every day, choose stones with a hardness of at least 7 to avoid scratches. For pieces intended for special occasions, softer stones may be suitable, provided they are handled with care and stored correctly.