Pearl grading,
made simple.
Begin with what you can see: the outline, reflections and surface. Then look at the pearl’s layers and how it works with its neighbors.
Our laboratory partner, GUILD, brings these observations together through five quality factors.
Our laboratory partner
The five qualities
Luster describes how light returns from the pearl. Within the same pearl type, brighter, better-defined reflections suggest stronger luster; soft, blurred reflections suggest lower luster. Compare pearls under the same lighting.
Surface quality is a separate observation. Turn the pearl and look at the number, size and visibility of its growth marks. A small mark does not necessarily dominate the way a pearl looks when worn.
- Very Good
- Near flawless
- Good
- Minor blemishes
- Fair
- Moderate blemishes
- Poor
- Heavy blemishes
These four descriptions are GUILD’s surface-quality categories.
Round, oval, drop and baroque describe a pearl’s outline. Shape grading considers regularity and symmetry within its form. A distinctive baroque pearl can still be a beautiful design choice.
Matching is considered when pearls are brought together in earrings, strands and suites. Their sizes, colors, shapes and luster should create a harmonious whole. Deliberate variation can also be part of the design.
GUILD describes shape, luster and matching using Very Good, Good, Fair and Poor. A type name, a favorite color or a larger diameter cannot replace that individual assessment.
Nacre is the pearl material around an implanted bead. Laboratories can assess the thickness of that layer; its quality and structure matter alongside the visible surface.
GUILD lists these reference minimums for high-quality assessment of bead-cultured pearls:
- Akoya
- ≥ 0.3 mm
- Tahitian
- ≥ 0.5 mm
- South Sea
- ≥ 0.8 mm
- Bead-cultured freshwater
- ≥ 0.8 mm
The freshwater reference applies to pearls grown around an inserted bead. Freshwater culture also produces non-bead pearls. Thickness alone does not determine an overall grade.
Reading the grade
GUILD combines shape, luster, surface, nacre and matching into three high-quality grades. The grade describes the combination, rather than a single feature.
- 5 starsNoble
- All five factors are rated Very Good.
- 4 starsMagnificent
- Nacre is Very Good. Of the other four factors, three are Very Good and one is Good.
- 3 starsSuperior
- Nacre is Very Good. Of the other four factors, two are Very Good and two are Good.
An alternative Superior combination allows Very Good shape and luster, Fair surface and Good matching, with qualifying nacre. Matching applies to groups of pearls.
Size and color also influence value. They describe part of what makes a pearl appealing, but a larger or darker pearl is not automatically a higher-quality pearl.
A trade name adds another layer of description. For example, Aurora is GUILD’s name for qualifying top-quality white freshwater cultured pearls graded Noble, with the required overtone. It is not the name of a pearl species.
A laboratory identification report and an overall quality grade answer different questions. Read the named issuer and the findings on the actual report.
PERLAVELLE benchmarks PL3, PL4 and PL5 to GUILD’s 3-star Superior, 4-star Magnificent and 5-star Noble standards. Japan’s Pearl Science Laboratory and China’s freshwater-pearl standards use different criteria and terminology; their grades should not be converted automatically.
PERLAVELLE selects only PL3 and above, benchmarked to GUILD’s three high-quality grades. Every pearl is considered individually.
Our Pearl Standards