The Mohs Scale: What is the Mohs Scale?

Gemstones have captivated humans for centuries with their beauty, durability, and diverse properties. When it comes to evaluating gemstones, their hardness is a critical factor. To assess and compare the hardness of different minerals, the Mohs scale of hardness was developed. In this blog, we will explore the fascinating world of the Mohs scale, its significance in the gemstone industry, and the ten minerals that form its foundation.

The Mohs scale, named after Friedrich Mohs, a German mineralogist, was introduced in 1812. This scale provides a standardised system for measuring the relative hardness of minerals by comparing their ability to scratch one another. The scale ranges from 1 to 10, with 1 being the softest and 10 being the hardest.

Let's delve into the ten minerals that serve as reference points on the Mohs scale, as well as their respective characteristics and applications:

Talc:

At the bottom of the scale is talc, which has a hardness of 1. Talc is extremely soft and can be easily scratched with a fingernail. It is commonly used in cosmetics and powders due to its smooth and absorbent properties.

Gypsum:

Next on the scale is gypsum, with a hardness of 2. Gypsum is a soft mineral that can be scratched by a fingernail. It is commonly used in the construction industry for making plaster and drywall.

Calcite:

With a hardness of 3, calcite is a relatively soft mineral that can be scratched by a copper penny. It is commonly found in limestone and marble and is often used as a decorative stone in architecture.

Fluorite:

Fluorite ranks at 4 on the Mohs scale. It is a colourful mineral that forms in a variety of hues. Due to its vibrant appearance, it is widely used in the manufacturing of jewellery, ornaments, and decorative items.

Apatite:

Apatite has a hardness of 5 and is a phosphate mineral that occurs in a variety of colours. It is commonly found in teeth and bones and is used in the production of fertilisers and in the manufacture of certain chemicals.

Orthoclase Feldspar:

Orthoclase feldspar has a hardness of 6. It is a common mineral found in igneous rocks and is widely used in the production of ceramics, glass, and as a component in building materials.

Quartz:

Quartz is one of the most abundant minerals on Earth and ranks at 7 on the Mohs scale. It is prized for its beauty, durability, and wide range of colours. Quartz is extensively used in the production of jewellery, watches, and various industrial applications.

Topaz:

Topaz, with a hardness of 8, is a silicate mineral that occurs in various colours, including blue, pink, and yellow. It is a popular gemstone and is often used in high-quality jewellery due to its excellent hardness and brilliance.

Corundum:

Corundum ranks at 9 on the Mohs scale and is known for its exceptional hardness and durability. It is composed of aluminium oxide and includes gemstones such as ruby and sapphire. Corundum is highly valued in the jewellery industry and is also used in various industrial applications.

Diamond:

At the top of the Mohs scale is the renowned diamond. With a hardness of 10, it is the hardest mineral known to mankind. Diamonds are treasured for their brilliance, fire, and durability, making them highly sought-after in the jewellery industry.

The Mohs scale is invaluable for evaluating and comparing the hardness of minerals. It allows gemologists, jewellers, and collectors to determine the durability and suitability of gemstones for specific purposes. For example, gemstones with higher ratings on the Mohs scale are more resistant to scratches and are ideal for everyday wear.

However, it is important to note that the Mohs scale only measures a gemstone's relative hardness and does not take into account other factors such as toughness, cleavage, or chemical resistance. Therefore, it is crucial to consider additional properties when assessing the overall durability of a gemstone.

In conclusion, the Mohs scale provides a standardised system for measuring the hardness of minerals, which is essential in the gemstone industry. From the delicate talc to the unmatched hardness of diamond, the Mohs scale offers a valuable reference point for understanding the durability and performance of gemstones. Whether you are a gem enthusiast, a jeweller, or simply curious about the world of minerals, the Mohs scale invites you to explore the captivating realm of gemstone hardness and appreciate the beauty and resilience of these remarkable treasures from the Earth.

We hope this has helped you understand what the Mohs Scale is, until next time jewellery makers!

-JM