Natural diamond grading involves assessing a diamond's quality and value based on the "Four Cs": Carat, Cut, Color, and Clarity. Carat refers to the diamond's weight, with one carat equaling 0.2 grams. Cut evaluates how well a diamond's facets interact with light, considering proportions, symmetry, and polish. Color grading ranges from D (colorless) to Z (light yellow or brown), with colorless diamonds being the most desirable. Clarity assesses the presence of internal inclusions or external blemishes, graded from Flawless (no inclusions or blemishes visible under 10x magnification) to Included (inclusions and/or blemishes visible to the naked eye). These factors together determine the diamond's overall quality, rarity, and market value, with higher grades in each category indicating a more valuable gemstone.

Carat weight measures a diamond's size, with one carat equaling 200 milligrams. Larger diamonds are rarer and typically more valuable. However, carat weight alone doesn't determine a diamond's worth; it must be considered with the other "Four Cs"—Cut, Color, and Clarity. Two diamonds of the same carat weight can differ significantly in value based on these other factors. Generally, as carat weight increases, the price per carat also rises due to the rarity of larger diamonds. Thus, while carat weight is a key indicator of size, its impact on value is closely linked to the diamond's overall quality.

The cut of a diamond is a critical aspect of its overall beauty and value, as it determines how well the diamond reflects and refracts light. Unlike the other "Four Cs" (Carat, Color, and Clarity), the cut is not about the diamond's inherent characteristics but rather how skillfully it has been shaped and faceted by the diamond cutter. The cut grade encompasses three main attributes: proportions, symmetry, and polish. Proportions refer to the angles and relative measurements of the diamond's facets, which affect its ability to handle light. Symmetry deals with the precision and alignment of the diamond's facets, ensuring that each facet is uniformly shaped and positioned. Polish refers to the surface quality and smoothness of the diamond facets. The cut is graded on a scale from Excellent to Poor, with an Excellent cut offering the best brilliance, fire, and scintillation. A well-cut diamond will appear more vibrant and lively, making it highly prized in the market.

Color in diamond grading refers to the presence of any hue in a diamond, with the ideal being completely colorless. The Diamond color scale ranges from D (colorless) to Z (light yellow or brown). Colorless diamonds (D-F) are the most prized, as they allow the most light to pass through, enhancing brilliance. As the grade moves towards Z, the presence of color becomes more noticeable, reducing the diamond's value. Thus, the less color a diamond has, the higher its quality and value.

Clarity in diamond grading assesses the presence of internal inclusions and external blemishes. The Diamond clarity scale ranges from Flawless (no inclusions or blemishes visible under 10x magnification) to Included (inclusions visible to the naked eye). Higher clarity grades mean fewer imperfections, which enhances the diamond's brilliance and value. While most inclusions are microscopic and don't affect the diamond's beauty, clarity is a key factor in determining its overall quality and worth.