Pearls and Pearl Grading
What this domain tests
Pearls and Pearl Grading tests pearl formation, cultured versus natural origin, saltwater and freshwater types, the GIA value factors, imitations, treatments, and care.
Core rules
- GIA evaluates pearls by seven value factors: size, shape, color, luster, surface quality, nacre quality, and matching. Luster is the sharpness of reflections; orient is the iridescent rainbow effect, not the same as bodycolor.
- Saltwater cultured pearls include Akoya (typically 2–10 mm), South Sea (roughly 8–20 mm), and Tahitian (roughly 8–14 mm). Freshwater pearls are usually tissue-nucleated and often irregular; saltwater pearls are usually bead-nucleated.
- Natural pearls formed without human intervention; cultured pearls formed with a nucleus or tissue implant. X-ray can reveal a bead nucleus; endoscopy can inspect the drill hole.
- Imitation pearls are coated beads of glass, plastic, or shell. The tooth test (gritty versus smooth) is only a hint; surface, drill hole, weight, and X-ray are stronger.
- Treatments include bleaching, dyeing, irradiation, coating, and luster enhancement; they must be disclosed.
- Care: avoid perfume, cosmetics, acids, heat, and ultrasonic cleaning; wipe with a soft damp cloth; restring knotted strands periodically.
Worked example
A 9.5 mm round white strand has mirror-like luster, faint pink overtone, minor surface blemishes, thick nacre, and a single bead nucleus visible on X-ray. Akoya cultured pearls commonly fall in this size range and are bead-nucleated; South Sea pearls are usually larger, and freshwater pearls are often tissue-nucleated and less perfectly round. The description should state cultured Akoya, not natural, and should note the faint overtone as a color description, not a treatment.
Traps
Do not use AAA or A as GIA grades; GIA uses descriptive factors. Do not assume large size alone means higher value-luster, nacre, and matching matter. Do not call orient color. Do not rely on the tooth test alone. Do not miss disclosure of dyeing or irradiation, and do not clean pearls ultrasonically.