The Mohs Hardness Scale Explained
2 Minute Read
When it comes to the longevity of gemstones, one of the most important factors to consider is their hardness, which is measured by the Mohs scale. This scale, ranging from 1 to 10, assesses a mineral’s resistance to being scratched, with diamonds at the pinnacle, scoring a 10. Understanding this scale is essential for anyone selecting jewellery, as it directly impacts the gemstone's durability and ability to maintain its brilliance over time.
To give you some context, here are a few gemstones and their Mohs score.
Diamond – 10
Sapphire/Ruby – 9
Topaz/Aquamarine/Emerald – 8-8.5
SPINEL - 8
Tourmaline/Garnet/Amethyst/Citrine - 7
Quartz - 7
Peridot - 6.5-7
Tanzanite - 6-7
Opal - 5.5-6.5
Pearl - 2.5-4.5
Gemstones are ranked on the Mohs scale according to their scratch resistance. A diamond, the hardest natural substance, tops the scale at 10, making it incredibly durable and resistant to wear. Below diamonds, sapphires and rubies score a 9, indicating they are also highly resistant to scratches, though not as tough as diamonds. Stones like topaz, aquamarine, and emeralds fall in the 8 to 8.5 range, while gems like tourmaline, garnet, amethyst, and citrine sit at 7.
What’s striking about the Mohs scale is the significant difference between the top rankings. The leap from a 9 to a 10 is enormous in practical terms. While diamonds remain nearly unscathed over time, even sapphires and rubies will show signs of wear, especially in high-contact jewellery like engagement rings. This durability is one of the reasons diamonds have been a popular choice for centre stones, ensuring that your piece retains its beauty for years, if not decades.
So, when choosing a gemstone, it’s wise to think about how your jewellery will look in a year or two. Is the unique colour of a softer stone worth the potential for surface damage? Sometimes it is, but it’s something to keep in mind.
There are also other considerations beyond hardness. While the Mohs scale measures scratch resistance, it doesn’t account for the potential of a stone to chip or fracture, especially if it has internal inclusions or flaws. For example, emeralds, which rate around 8.5, are notorious for their internal inclusions. These can make them prone to chipping or cracking, despite their relatively high hardness. This is why it’s crucial to consider the overall integrity of a gemstone, not just its Mohs score, when selecting a piece of jewellery.
In the end, understanding the Mohs scale helps you make informed decisions, ensuring that your jewellery not only looks stunning but also stands the test of time. Your jeweller should guide you through these factors during the design process, but it’s always good to have this knowledge as you explore your options.
