Diamonds have long been celebrated for their exceptional hardness and unrivalled beauty.
They are renowned for their use in jewellery and have a reputation for being the hardest natural substance known to man. But are diamonds truly the hardest substance on Earth?
In this article, we will explore the science behind diamond hardness, how it is measured, and whether there are any substances that can rival or exceed the hardness of diamonds.
Understanding Diamond Hardness
1. The Mohs Scale of Hardness
The hardness of minerals is measured using the Mohs scale, developed by Friedrich Mohs in 1812.
The scale ranks minerals based on their ability to scratch other substances, ranging from 1 (talc) to 10 (diamond).
On this scale, diamonds sit at the top with a rating of 10, indicating they can scratch all other minerals but cannot be scratched by any other material ranked lower on the scale.
2. Atomic Structure of Diamonds
The remarkable hardness of diamonds is due to their unique atomic structure. Diamonds are composed of carbon atoms arranged in a crystal lattice structure.
Each carbon atom forms strong covalent bonds with four other carbon atoms, creating a rigid three-dimensional network. This structure gives diamonds their incredible hardness and resistance to scratching.
Are There Harder Substances?
While diamonds are the hardest natural substance on the Mohs scale, scientific advancements have led to the discovery of materials that exhibit hardness exceeding that of diamonds under certain conditions.
1. Aggregated Diamond Nanorods (ADNR)
Aggregated Diamond Nanorods, also known as hyperdiamond, are a synthetic material created by compressing fullerene (a form of carbon) under extreme pressure.
ADNR has been found to be harder than natural diamonds, making it one of the hardest known materials.
2. Wurtzite Boron Nitride (w-BN)
Wurtzite Boron Nitride is another material that, in its pure form, can exceed the hardness of diamonds.
W-BN has a similar structure to diamond but is composed of boron and nitrogen atoms. Under certain conditions, it can exhibit a hardness greater than that of diamond.
3. Lonsdaleite
Lonsdaleite, also known as hexagonal diamond, is a rare form of diamond with a hexagonal lattice structure instead of the typical cubic arrangement.
It is formed under extreme conditions, such as those found in meteorite impacts.
Lonsdaleite is theorised to be harder than regular diamonds, although it is extremely rare and not typically found in commercial applications.
Practical Applications of Diamond Hardness
1. Jewellery
Diamonds are highly valued in jewellery not only for their brilliance and beauty but also for their durability. Their hardness makes them resistant to scratching, ensuring that diamond jewellery retains its lustre and appearance over time.
2. Industrial Uses
The exceptional hardness of diamonds makes them invaluable in industrial applications. Diamonds are used in cutting, grinding, and drilling tools for materials that are too hard for other substances to handle.
Synthetic diamonds, in particular, are widely used in these applications due to their cost-effectiveness and consistency in quality.
3. Scientific Research
Diamonds are also used in scientific research, particularly in high-pressure experiments. Diamond anvil cells, which use diamonds to generate extremely high pressures, are crucial in studying the behaviour of materials under extreme conditions.
Conclusion
Diamonds are indeed the hardest natural substance on Earth according to the Mohs scale of hardness. Their unique atomic structure gives them unparalleled hardness and durability, making them highly valued in both jewellery and industrial applications. However, advancements in materials science have led to the discovery of synthetic materials like Aggregated Diamond Nanorods and Wurtzite Boron Nitride that can exceed the hardness of natural diamonds under specific conditions. While diamonds remain unmatched in nature, these discoveries open new possibilities for materials with even greater hardness.