Pearl Surface Grade — Clean
Pearl Surface Grade — Clean
GIA's top surface grade, for pearls without visible blemishes
Clean is the highest of the four surface-quality grades in GIA's pearl grading system, indicating a pearl whose nacre presents no blemishes visible to the unaided eye, or only minor imperfections detectable on close inspection. The category sits above Lightly Spotted, Moderately Spotted, and Heavily Spotted, and is the rarest grade by a substantial margin in cultured production.
What Clean means in practice
A Clean-grade pearl shows smooth, uninterrupted nacre with no pits, cracks, abraded patches, or discolouration evident at normal viewing distance. Under a 10x loupe a Clean pearl may still show some surface character — fine wrinkles, a faint growth line, microscopic bumps from the bead nucleation site — but nothing that disrupts the eye when the pearl is mounted and worn. The grade is awarded to the pearl as a whole; trace features that would fail a stricter standard at the bench can still be present on a stone graded Clean.
The grade is most often achieved by Akoya and freshwater pearls, where smaller body sizes and shorter culture cycles favour smoother nacre. Larger South Sea and Tahitian pearls are correspondingly less likely to grade Clean; the longer culture period and the larger surface area expose the pearl to more biological insults, and a Clean South Sea or Tahitian pearl is genuinely scarce.
Premium and trade usage
Clean-grade pearls command significant premiums. For Akoya strands the differential between Clean and Lightly Spotted may be 30 to 50 percent of value at equivalent size and lustre. For South Sea and Tahitian pearls the differential widens — large round Clean South Sea pearls of fine lustre are auction-grade material, and individual specimens can carry premiums of several multiples over Lightly Spotted equivalents.
Within the Clean category itself the trade distinguishes informally between fully Clean and what is sometimes called eye-clean or blemish-free — pearls that show no surface character even under loupe inspection. These exceptional stones, which GIA still grades as Clean, are reserved for the very highest tier of jewellery work.