Good is the third tier in GIA's five-step pearl lustre scale, positioned below Excellent and Very Good and above Fair and Poor. A Good lustre describes a pearl with bright, recognisable surface reflections whose edges are slightly hazy or soft rather than crisp. The light source reflected on the nacre is clearly visible — there is genuine brilliance — but the image lacks the sharp, mirror-like definition that distinguishes the top two grades. Good is the working ceiling of much of the mid-market cultured-pearl trade and accounts for a substantial share of commercial production across akoya, Tahitian, South Sea, and freshwater categories.

What Good lustre looks like

Under daylight-balanced light at arm's length, a Good-grade pearl shows a bright reflection of the light source. The shape of a fluorescent tube or window mullion is recognisable in the curve of the pearl, but the edges of that reflection blur slightly into the surrounding nacre rather than terminating sharply. The pearl looks bright and alive, but does not produce the near-perfect mirroring of an Excellent grade. Compared with Very Good, the difference is one of crispness rather than brightness; compared with Fair, the difference is one of clarity of image.

Underlying causes

Good lustre typically corresponds to nacre thickness in the range of about 0.35 to 0.5 millimetres in akoya production, with adequate nacre platelet ordering and a generally clean surface. Minor surface texture, faint haziness from sub-surface inclusions, or a slightly disordered outermost nacre layer reduce sharpness without eliminating brightness. The host environment during the final months of cultivation has an outsized influence: cooler water and longer cultivation tend to produce tighter platelet stacking and crisper reflections, pushing lustre toward Very Good or Excellent.

Identification

GIA's lustre assessment is performed at arm's length under controlled illumination, on the cleanest portion of each pearl. The grader records how brightly and how sharply the light source is reflected. Good-grade pearls show clearly visible reflections with soft edges; the reflected image's outline is identifiable but not crisp.

For a strand, the grade is taken from the bulk of the pearls rather than from the best or worst individuals, with allowance for a small number falling on either side of the central band. Two strands graded Good can differ in absolute brightness depending on body colour, overtone, and surface state, but both will share the soft-edged reflection that defines the grade.

In the trade

Good-lustre pearls are the workhorse of the mid-market. They appear widely in mall jewellery, mainstream retail, and online channels where price competitiveness is the priority. Akoya strands at Good lustre typically trade at thirty to fifty per cent below Excellent-grade equivalents of the same size and shape, with steeper discounts where overtone or surface quality further compromise the strand. Tahitian and South Sea production at Good lustre still commands meaningful prices because of the underlying scarcity of larger pearls, but the gap to higher-grade material is similar in proportion.

For buyers, Good lustre represents acceptable commercial quality for everyday wear and for designs where the pearl is not the dominant element of the piece. Where the pearl is the centre of the design — a classic strand for formal occasions, a single-pearl pendant, a high-end bridal piece — clients who can stretch to Very Good or Excellent will see the difference at a glance and feel it in the resale market years later.

Care

Pearls at any grade benefit from regular wiping with a soft cloth after wear, isolation from perfumes and cosmetics, and storage away from harder gem materials. Good-grade strands strung on silk should be restrung every two to three years with regular wear to prevent stretch and breakage at the knots.

Further reading

• GIA — Pearl Quality Factors
• GIA Gems & Gemology — pearl grading and lustre articles
• International Gem Society — pearl grading reference