The quality and grading of a pearl is assessed using several key characteristics, including lustre, surface quality, shape, size, colour and nacre thickness. Of these, lustre is often considered the most important, as it determines how brilliantly a pearl reflects light and showcases its natural radiance. While no two pearls are identical, those with a bright lustre, smooth surface, thick nacre and well-balanced shape are generally regarded as the most desirable. Together, these characteristics form the foundation of the pearl grading system used throughout the industry.