As a geologist with a strong interest in mineralogy, I can tell you that the hardest mineral in the universe is often considered to be diamond. Diamond is renowned for its exceptional hardness, which is rated as 10 on the Mohs scale of mineral hardness. This scale ranges from 1 (talc, the softest mineral) to 10 (diamond). The hardness of a diamond is due to its tightly bonded carbon atoms arranged in a crystal lattice structure.

Diamonds are not only the hardest natural material known to humans but also have a high refractive index and strong thermal conductivity, making them valuable for industrial applications and as gemstones. They are commonly used in cutting, drilling, and grinding tools due to their hardness.

However, it's important to note that while diamonds are the hardest natural mineral, there are synthetic materials that can be even harder. For example, wurtzite boron nitride is a synthetic material with a structure similar to diamond and is considered to be harder than diamond under certain conditions. But since the question specifically asks about minerals in the universe, and considering the context usually refers to natural substances, the answer remains diamond.

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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.read more >>