HOW TO GRADE A PEARL


 PtterGrading

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 five levels: Low, Good, 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. AAA+ 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 good to medium luster. Pearls with a very low luster look very milky or chalky. They show very little highlights.

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+ and AAA grade Akoya pearls have very thick nacre (0.4mm and up) AA+ and AA grade pearls have thick nacre (0.25 to 0.4MM), A+ and A grade pearls have medium nacre (0.2 to 0.25MM). Pearls with very 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 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. AAA+ 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 slightly blemished to lightly 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.

Pearl Shape

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 ovalish.

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 AAA+, 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, grey, 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 grey. AAA+ and AAA grade Akoya pearls are white or pink body color with rose or grey overtone. AA+ and AA grade pearls are white, or light cream body color with rose, grey or light green overtone. A+ and A grade pearls are white, medium cream, or pink body color with rose, grey or green overtone.


 
 
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