The Mohs Hardness Scale 101
As you explore the world of gemstones and jewellery, one of the first things you'll encounter is the Mohs Hardness Scale—the key to understanding a stone’s durability and daily wearability! The scale of one to ten, from softest to hardest, measures the hardness of a stone in relation to other minerals.
A ten, for example, is capable of scratching all other stones below it, but would not be able to be scratched in return. This does not mean that the stone is indestructible. The hardness of a stone is what it can resist on the surface. It’s not the same as the stone’s toughness, which tells us how strong the stone is against pressure, temperature, and force.
But what does all of this mean in terms of your favourite stones and their everyday wear? Let’s break it down, starting with our softest stones and going up to the famous, durable diamond!
Please keep in mind that things such as stone setting, cut, and lifestyle can greatly impact the wearability and life span of a piece, regardless of its hardness level.
2.5: The Delicate Pearl
While the hardness scale covers all kinds of minerals and stones, the softest stone that we commonly see in jewellery is pearl. These delicate stones are highly susceptible to environmental damage such as aging, dehydration, chemical exposure, and burning. They should only ever be cleaned with warm soapy water, and completely dried before wearing again, and worn with caution.
5 - 6.5: The Soft Stones: Opal, Moonstone, Sunstone, Labradorite
Opals and stones within the feldspar family (moonstone, sunstone, labradorite, etc) all have a range of hardness levels as the composition and formations of these stones can vary based on environmental factors such as water and bacteria!
These stones also have a poor toughness level. Due to this extra caution should be taken when wearing these stones, and they should be removed before doing chores or any laborious activity to prevent damage.
6.5 - 7: The Semi-Soft Stones: Tanzanite, Agate, Quartz
Tanzanite, and stones within the quartz family like agates, and amethyst, are all fairly soft stones, but are a bit more durable than the other stones that have been looked at so far. These stones are not as affected by natural factors such as water and light, but can still be compromised by chemicals. They should be cleaned only with warm soapy water, and it is still encouraged that they be removed before any physical activity to prevent damage.
8: Durable stones: Topaz
Topaz is high enough on the hardness scale that it is resistant to daily wear and tear, however its low toughness rating means the stone is still susceptible to damage against sudden temperature changes, pressure, and force. When wearing this stone, you should always be careful of any abrasive solutions and surfaces that may interact with it.
9: Hard stones: Sapphire, Ruby
Sapphire and ruby are both stones in the corundum family, and are hard and tough stones. They make an excellent alternative to diamonds for wedding jewellery, are known for their ability to resist every day wear and tear, as well as holding up under steam cleaners and Ultrasonics. The higher the quality of the stone, the more durable it will be. Corundum stones with fractures, inclusions, dyes, and cavities can cause the stone to be more susceptible to chemicals and acids.
10: The Illustrious Diamond
Although there is only one scale difference between corundums and diamonds, diamonds are significantly harder than sapphires. As a 10 on the hardness scale, diamonds can only be scratched by other diamonds. The toughness of a diamond can correspond with the quality of the diamond and whether or not it has inclusions. While the stone is incredibly resistant to scratching and chemicals, it may still crack, fracture, or chip under high pressure, and extreme heat. And they attract dirt and oils like nobody's business!
