South Sea cultured pearls are pearl concretions that are secreted inside the silver- or gold-lipped Pinctada maxima species of pearl oysters cultivated mainly in Australia, Papua New Guinea, Indonesia, the Philippines, Thailand, and Myanmar (Burma).

There is no standard South Sea pearl grading standard and each individual company has its own standards. The South Sea Pearl Consortium, the trade association of South Sea Pearl farmers and distributors, uses five grading standards. South Sea Legend by Pearl Oasis uses those five standards, plus a sixth, nacre thickness. The following is the standard that we uses. If you look at the details of an South Sea pearl item in our catalog, you will find a detailed listing showing how the item rates for each of the six grading standards. Most other on-line pearl jewelry websites give no quality information about their products.

Six Grading Factors

There are six grading factors we use to grade South Sea pearls:

1. Shape: Round, Semi-Round, Semi-Baroque, Ringed or Circle, Baroque.
2. Size: 8MM to 18MM.
3. Surface Quality: Clean (A), Light Blemished (B), Moderately Blemished (C), Heavily Blemished (D).
4. Luster: Very high (AAA), High (AA), Medium (A), Soft (B).
5. Nacre Thickness: Thick, Thin.
6. Color: Body color plus overtone.

South Sea pearls have five different shapes: Round, Semi-Round, Semi-Baroque, Ringed or Circle, Baroque.

Round pearls are almost perfect spheres whose diameter variation rate is less than 2%. The round pearl is the most sought after and the most rare of South Sea cultured pearls. The most beautiful and, therefore, the most in demand are perfectly round pearls.

To determine whether a pearl is round, a professional tester rolls it across a table. If it rolls straight, it is round. If the pearl veers off more than slightly, it is semi-round.

Semi-round pearls are slightly imperfect spheres whose diameter variation rate is greater than 2% but less than 5%. Also called as off round or near round.

Semi-baroque pearls exhibit at least one axis of rotation (can be spun on a table top) and are subdivided into four shapes: drop, button, pear and oval.

Ringed, or circled pearls are characterized by regular streaks, rings or grooves that are perpendicular to an axis of rotation and cover more than a third of the pearl's surface. Ringed pearls generally account for 25-30% of a South Sea cultured pearl harvest.

Baroque pearls do not have any axis of rotation (cannot be spun on a table top).

Size

Pearls are classified from millimeter to millimeter (no fractional millimeters). Round and off round pearls are measured by the shortest diameter. All pearls in other shapes are measured along two diameters (the longest and second longest). South Sea pearls generally range between 8mm and 14mm. Some pearls reach 16mm and very exceptionally 18mm. To date, the record diameter is 20mm. Pearls that reach the extraordinary size of 20mm, which no matter what their color make them exceptional gems.

Surface Quality

We use four ratings for South Sea cultured pearl surface quality: Clean (A), Lightly Blemished (B), Moderately Blemished (C), Heavily Blemished (D). All surface grading is done with the naked eye (no magnification device like a jeweler's loop).

Quality A pearls are clean. These pearls are entirely smooth or are marred with just one or two tiny ripples or indentations (often hidden later by a drill hole) that are visible to the naked eye but are confined to less than 10% of the surface. If these pearls also have very good luster, they are very rare. Their extreme rarity adds significantly to their cost.

Quality B pearls are lightly blemished. These pearls are have some imperfections concentrated over less than a third of their surface.

Quality C pearls are moderately blemished. These pearls have light concentrations of imperfections over less than two-thirds of their surface.

Quality D pearls are heavily blemished. These pearls have light imperfections over more than two-thirds of their surface and no deep imperfections; or deep imperfections over half of their surface .

Luster

Luster is also a factor of pearl surface quality. South Sea pearls are famous for their high gloss luster. We have four grades of pearl luster: Very High (AAA), High (AA), Medium (A) and Soft (B).

This is the quality of the light reflections from the pearl's surface. Pearls are said to have high, or very high, luster when the reflections are bright and sharp. When the light reflections are weak and fuzzy (or diffused), the pearls are described as soft or dull. Dull luster pearls are rejected.

Nacre Thickness

Nacre thickness affects the durability and sometimes the beauty of a South Sea cultured pearl. South Sea pearls have a reputation of having thick nacre due to their long culturing period.

Color

South Sea pearl color is natural. South Sea pearls can take on all the colors of the rim of the silver- or gold-lipped oyster shell which produces it. South Sea pearls have a wide range of body colors. The predominant basic colors of a South Sea pearl are white, gray, blue, cream and gold. South Sea pearls also have the beautiful overtones: blue, pink, gold, and silver. These overtones may be present in a variety of combinations and are considered a plus factor.