Diamonds are well-known for their exceptional physical properties. They are incredibly hard and durable, ranking a 10 on the Mohs scale of mineral hardness. This means that they can resist scratches and chips better than any other material. Diamonds also have a high refractive index, which gives them their characteristic brilliance and fire. They are also highly resistant to heat and chemicals. All of these physical properties make diamonds an ideal choice for engagement rings, jewelry, and industrial applications.

When it comes to grading diamonds, there are several factors that are taken into consideration. The 4Cs - cut, color, clarity, and carat weight - are used to assess a diamond's quality and value. The cut refers to the diamond's proportions, symmetry, and polish, which affects how well it reflects light. Color is graded on a scale from D (colorless) to Z (yellow or brown tint). Clarity refers to the presence of any internal or external flaws, while carat weight is simply a measure of the diamond's size. A combination of these factors determines a diamond's overall grade and value.