Cultured pearls from Japan
Established 1995
Phone: 703-683-2678
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How we grade Akoya (salt water) cultured pearls

GIA Pearl Grading SetWe follow the cultured pearl value standards provided by the Gemological Institute of America (GIA) and The Guide for Grading Akoya Cultured Pearls by Gemworld International, Inc. We use the G.I.A. Gem Pearl Master Comparison Set (to see the comparison set, click here) to actually compare with the pearls we grade. The G.I.A. Gem Pearl Master Comparison Set was developed by Gemworld International, Inc. and International Cultured Pearls of The Orient, Inc. for G.I.A. and exclusively provided by G.I.A.

Akoya is the Japanese word for salt water. In the jewelry trade, Akoya pearls or Akoya cultured pearls are known as salt water cultured pearls.

What does the "Letter Grade" mean?

There are no standard or objective grading systems for pearls. Every company can establish their own system. Proper grading is done by comparing pearls against a master comparison pearl set.

G.I.A. lists six value factors for pearls: luster, nacre thickness, surface quality, shape, color, and matching. Pearl worth depends on the combination of these six value factors and the "letter grade" is an attempt to give a single designation that fairly expresses the combination of these six factors.

All the pearl jewelry at Pearl Oasis has a "letter grade", but we also list our determination for each of the six factors. If you go to the "details" page of an item, you will see the grading for each of the six factors.

Below is a brief introduction of the Akoya pearl grading system we employed along with what each of the six factors must be to earn a given "letter grade".

Grade Luster Nacre Thickness Surface Quality Shape Color Matching
A to A+ Medium Thin Noticeable
Off Round
Mostly Round
White, Medium Cream, or Pink Body Color
Rose, Gray, Green
AA Medium
Medium Slightly
Round White, Light Cream, or Pink Body Color
Rose, Gray, Green
Very Good
AA+ High
Very High
Very Slightly
Round White, Light Cream, or Pink Body Color
Rose, Gray, Green
Very Good
AAA Very High Thick Very Slightly
Round White, or Pink Body Color
Rose, Silver Gray
Very Good

Note that Pearl Oasis does not carry A to A+ grade Akoya cultured pearls. The following is a detailed explanation of each factor.

Pearl Luster

Pearl luster is the surface brilliancy of pearls. It is probably the best expression of a pearl's beauty. Luster does not simply mean a shiny surface It implies the structural beauty of the nacre.

We grade pearl luster in six levels: Very Low, Low, Medium, High, Very High and Excellent. Pearls with a very high luster will generally show strong and sharp light (mirror like) reflection of the light source. AAAA and AAA grade Akoya pearls have excellent to very high luster. AA+ and AA have high to good luster. A+ and A grade pearls have medium luster. Pearls with a very low luster look very milky or chalky. They show very little highlights. Pearl Oasis rejects pearls with very low luster.

Pearl Nacre Thickness

Nacre is the coating that the oyster forms around the nucleus of the pearl. Nacre thickness is more than the amount of nacre. It has other meaningful aspects as well. The structure of the nacre is composed of thousands of layers of thin calcium carbonate crystals. This distinctive nacre structure influences the color, luster, durability and elasticity of the pearl.

AAA grade Akoya pearls have very thick nacre. AA+ and AA grade pearls have medium thick nacre. A+ and A grade pearls have thin nacre. Pearls with thin nacre allow the core nuclei to be seen through the nacre. Pearls with thin nacre often exhibit visible cracks in the nacre. Pearls with thin nacre can also display signs of nacre peeling or chipping. Pearl Oasis rejects such pearls and we do not carry them.

Pearl Surface Quality

All the factors that disturb the surface smoothness of the pearl and hence decide its appearance are called blemishes and imperfections (also called spots or flaws). The quality of the pearl is greatly affected by blemishes. Natural blemishes are formed during pearl cultivation. By definition, a blemish is anything that can be seen by unaided eyes.

When grading an individual pearl (for a pearl ring, or pearl pendant, for example), the degree of blemish is divided into clean, slight spot, medium spot and heavy spot according to number, size, kind and location of the blemish. We reject pearls that exhibit excessive amounts of blemishes, such as cracks throughout the pearls, prominent flaws in a single pearl, patches of missing nacre, obvious discoloration's throughout the pearls, and flaws which cover the majority of the surface of the pearls.

When grading a whole strand of pearls (for a necklace, for example), we determine what percentage of pearls have blemishes. The less such pearls the better quality of the strand. We grade surface quality of a pearl strand by determining what percentage of pearls have blemishes. AAAA and AAA grade Akoya pearls are unblemished to very slightly blemished pearls. AA+ and AA grade pearls are very lightly blemished to slightly blemished pearls. A+ and A grade pearls are noticeably blemished. For a strand of pearls, 0-5% pearls with blemishes is considered unblemished to very slightly blemished. 10-20% is very slightly blemished, 20-30% is slightly blemished to lightly blemished. We reject pearl strands that have more than 40% of the pearls with blemishes.

Pearl Shape

When it comes to round shape, no other cultured pearl can compete with the Akoya cultured pearl.

We grade pearl shape into five levels:

  1. Semi-baroque and baroque
  2. Off round
  3. Slightly off round
  4. Mostly round
  5. Round

Semi-baroque and baroque are pear-shaped or irregular shaped and are listed separately. Off-round pearls have flattening on one side or are oval.

If the pearl's shape is graded less than round, the pearl will only qualify for grade A+ or A. Only round pearls will qualify for a grade of AAAA, AAA, AA+, or AA.

Pearl Color

Pearl color is a combination of body color and overtone. Body color is the predominant basic color of the pearl. When pearls lay on a white surface, body color can be best seen on the outer edge of the pearl. Body colors include white, light pink or pink, light cream, medium cream and dark cream, yellow or golden. Overtone is one or two colors that overlie the body color. When inspecting pearls under light, you may see color in the central dark areas of the pearls. This is the overtone. Overtone colors include rose, gray, and green. You should remember that pearl color for the purposes of grading is not a measure of the beauty of pearls or your choice of pearl color. Pearl color relates to an aspect of pearl quality measured by pearl color. It is important to remember that what color of pearls is the most desirable in one market or culture may not be desirable in another.

With Akoya cultured pearls, the color and intensity of the color is a distinguishing feature of pearl quality. Low quality pearls often have brown or yellowish body color and do not have overtone or very poor overtone. Pearls without overtone look "flat". High quality pearls have deeper overtone color, because the intensity of color is the result of thick nacre and high luster. Pearl processing also effect pearl color.

Generally, Akoya pearls have four basic body colors: white, cream (ranging from light, medium or dark), pink and yellow and three overtones: rose (pinkish), light green and gray. AAAA and AAA grade Akoya pearls are white or pink body color with rose or gray overtone. AA+ and AA grade pearls are white, or light cream body color with rose, gray or light green overtone. A+ and A grade pearls are white, medium cream, or pink body color with rose, gray or green overtone. Akoya pearls with dark cream, or yellow body color are lowest quality and are not used by Pearl Oasis.

Pearl Matching

Matching refers to how closely two or more pearls are similar in luster, nacre thickness, surface quality, shape, and color plus size of the pearl. Matching applies to pairs of pearls and strands of pearls but does not apply to jewelry with a single pearl. AAAA and AAA grade Akoya pearls are excellent to very good matching. AA+ and AA grade Akoya pearls are very good to good matching. A+ and A grade Akoya pearls are good matching. We do not accept poorly matched pearl pairs or strands.

Put All Pearl Factors Together

Pearl worth depends on how one combines the complete mix of these six value factors. Two strands of pearls of exactly the same size maybe very different in other factors such as different color, different surface quality. Additionally, not each of the factor are weighted same. According to Gemworld International's Pearl Guide, the following percentages apply to the six factors except size:

Luster 25%
Nacre Thickness= 25%

Surface quality = 20%
Shape = 15%
Color = 10%
Matching = 5%.

Total 100%

Pearl Size

While pearl size is not one of the six quality factors, it is a component of the "matching" factor. For Akoya cultured pearls, size means the pearl's diameter measurement. Pearl size is expressed in millimeters, rounded to the nearest 0.5MM. Akoya cultured pearls range from 2MM to 11MM. Most common sizes are from 5MM to 8MM. A 10MM Akoya is uncommon, and an 11MM Akoya is rare.

In a strand of pearls, if individual pearls are within the .5mm range, they are considered the same size. When you see a size range like "6.5 to 7mm", it means that no pearl in the strand will be less than 6.5mm or greater than 7mm.

Generally, if other value factors are equal, the value of Akoya cultured pearls rise with their size. However, small size akoya cultured pearls can cost more than larger sizes.

The larger the size of an akoya cultured pearl, the more difficult it is to produce a pearl with high luster, nacre thickness and good surface quality.

To help you visualize how big a 7MM pearl is, see our Pearl Size Page.


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Pearl Oasis
PO Box 2631, Alexandria, Virginia 22301 USA
Phone: 703-683-2678

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