As a material science expert, I have a deep understanding of the properties and behaviors of various substances. When we talk about the hardness of materials, we are often referring to their resistance to deformation, scratching, or abrasion. The Mohs scale of mineral hardness is a qualitative scale that characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. On this scale, diamond is rated as the hardest known natural material, with a hardness of 10.

However, the statement that a diamond is the "hardest substance on earth" is not entirely accurate. While diamond is indeed the hardest natural material, there are synthetic materials that are harder. For instance, the material you mentioned, wurtzite boron nitride, is an example of a synthetic material that can be harder than diamond under certain conditions. Wurtzite boron nitride has a similar structure to diamond, but it is composed of boron and nitrogen atoms instead of carbon. This difference in atomic composition can lead to variations in hardness.

Another interesting point is lonsdaleite, also known as hexagonal diamond. It is a form of carbon with a hexagonal crystal structure, different from the more common cubic structure of diamond. The arrangement of carbon atoms in lonsdaleite is distinct, which can affect its hardness properties. However, it is important to note that while lonsdaleite is rare and has been found in meteorite impact sites, its hardness relative to diamond is still a subject of some debate.

It's also worth mentioning that the hardness of a material can be influenced by more than just its atomic structure. Factors such as impurities, crystal defects, and the direction of the applied force can all play a role in determining a material's hardness.

In conclusion, while diamond is the hardest natural material known, the title of the "hardest substance on earth" is not as straightforward as it might seem. The hardness of a material is a complex property that can be influenced by a variety of factors, and there are synthetic materials that may surpass diamond in hardness under certain conditions.

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The first, wurtzite boron nitride has a similar structure to diamond, but is made up of different atoms. The second, the mineral lonsdaleite, or hexagonal diamond is made from carbon atoms just like diamond, but they are arranged in a different shape.Feb 16, 2009read more >>