In pearl grading, the term lightly blemished describes a surface condition where minor imperfections are present but limited in extent, typically affecting less than approximately 10 percent of the visible surface area when the pearl is set or oriented for viewing. The grade sits between clean (effectively flawless surface) and moderately blemished, and corresponds approximately to the GIA pearl description grade of A or AA depending on the system in use.

Grading systems and terminology

Pearl surface grading is not standardised internationally to the degree that diamond clarity grading is. The GIA Pearl Description System uses the surface descriptors clean, lightly blemished, moderately blemished, and heavily blemished, with each based on the proportion and prominence of surface characteristics. The Tahitian Pearl Producers Association uses an A through D system in which A and B both correspond approximately to lightly blemished. The Japanese Hanadama certification, issued by the Pearl Science Laboratory of Japan for akoya pearls, requires a surface grade equivalent to lightly blemished or better.

The characteristics that fall within the lightly blemished category include minor pinpoints, faint surface marks, very small bumps or hollows, and superficial discolouration. Cracks, exposed nuclei, large pits, and any feature that affects durability disqualify a pearl from this grade regardless of the proportion of surface affected.

Trade significance

Lightly blemished is the most common commercial grade for fine cultured pearls. Truly clean pearls, particularly above 8 millimetres, are rare in any production run, and a strand entirely matched at clean grade commands a substantial premium over an otherwise identical lightly blemished strand. Akoya production from Japan, South Sea production from Australia and the Philippines, and Tahitian production all yield the majority of their fine-grade output at lightly blemished. For the buyer, the practical question is the location of the blemishes: those concealed by drilling or by the setting are commercially equivalent to clean.

Inspection and disclosure

Surface grading should be performed under diffuse daylight or a 5500 K daylight lamp, with the pearl rotated through its full surface. The GIA Pearl Description System and the auction-house catalogues at Christie's and Sotheby's both disclose surface grade as one of the seven value factors. A lightly blemished disclosure on a fine South Sea or Tahitian strand should not be read as a quality concern; it is the realistic expectation for nature-influenced material.