What measurement unit is used to indicate the dimensions of a diamond?

The dimensions of a diamond are typically indicated in millimeters. This unit of measurement is precise and suitable for the small sizes of gemstones, allowing for detailed and accurate assessments of length, width, and depth. Since diamonds are often quite small, millimeters provide a practical scale that supports the standards used in the jewelry industry for both retail and appraisal purposes.

Other measurement units, such as inches and centimeters, are less common for this specific application due to their comparatively larger scales, which may not capture the finer details required for precise measurements in gemstones. Micrometers could theoretically be used for very fine measurements, but they are mainly used in specialized scientific contexts rather than standard gemology practices. Thus, millimeters remain the most appropriate and widely accepted unit for indicating the dimensions of diamonds.