Cultured Pearl Grading System: Akoya, Tahitian & South Sea Nacre Thickness & Overtone Luster
By Artisanal Silversmithing & Gemology Review Board
Demystifying pearl quality: the GIA 7 value factors, Japanese Akoya mirror lusters, French Polynesian black Tahitian pearls, Australian Golden South Sea sizes, and freshwater durability.
Pearls are organic gemstones produced by living mollusks, evaluated through nacre thickness, surface perfection, overtone color, and deep mirror reflectivity.
1. The Four Major Cultured Pearl Varieties
Pearl Variety
Typical Size Range
Natural Body Colors & Overtones
Luster Characteristics
Japanese Akoya
5.0 mm – 9.0 mm
White, cream, silver with pink/rose overtones
Sharpest, most mirror-like metallic luster
Tahitian (Black Pearls)
8.0 mm – 16.0 mm
Peacock green, aubergine, charcoal, silver
Rich iridescent exotic orient
South Sea (White & Gold)
9.0 mm – 20.0 mm
Satin white, champagne, intense 24K gold
Deep satiny glow with thickest natural nacre
Freshwater Cultured
4.0 mm – 12.0 mm
White, lavender, peach, pink pastels
100% solid nacre; highly durable for everyday necklaces