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Japanese Akoya Pearl Grading

Updated: May 12, 2022

Japanese Akoya pearls range in size from as small as 2mm to as large as 10mm. Pearls below 6.0mm in size are considered to be on the smaller side, while anything between 6.0mm and 8.0mm are common sizes selected for pearl jewellery items. Akoya pearls sized above 8.0mm are considered to be above average in size, and such pearls are more rare and valuable.

Pearl grading is a key metric to understand before ultimately making your pearl jewellery purchase. Akoya pearls are graded using the Japanese Pearl Grading System, using the A - AAA Scale with the addition of Hanadama Akoya pearls representing the highest pinnacle of the pearl type.

The A - AAA system evaluates pearls according to Surface Quality, Luster, and perfection of Shape (roundness and symmetry). Akoya pearls are also graded on Nacre Thickness, which is a visual inspection completed by the grader rather than via x-ray analysis. The only exception to this is for Hanadama pearls which are x-rayed at the Pearl Science Laboratory in Tokyo.








Low Quality Japanese Akoya representing the bottom 50% of pearl harvest (Not Sold at Pearl Source.

Medium-Grade Japanese Akoya representing top 60% of Harvest. Commonly found at jewellery stores and Major Department Stores (Not Sold at Pearl Source).

High-Grade Japanese Akoya representing the top 5-10% of a pearl harvest. Found in Finer Jewelry Stores.

Very High-Grade Japanese Akoya representing the top 1-5% of a pearl harvest.

Gem Quality Japanese Akoya Pearls representing the highest 1% of a pearl harvest. Accompanied by a numbered certificate by the Pearl Science Laboratory of Japan.


Heavy blemishing with only a 50% or less clean surface.

Minor to medium blemishing with a 70-80% clean surface.

Minor blemishing with at least 90% of the pearl surface clean.

Very Minor to no blemishing with at least 95% of the pearl surface clean.

99% or cleaner pearl surface with either very minor to no blemishes visible.





Very High






Very Thick

Very Thick


Round/Off Round


Perfectly Round

Perfectly Round

Perfectly Round

SURFACE BLEMISHING - Pearls that feature clean surfaces without inclusions like pin-pricks, scoring marks, chalky spots and wrinkles will be much more highly valued than pearls with multiple blemishes. Because pearls are a product of nature however, there will always be some form of blemish - even if you can’t view them with the naked eye. This is why we will never call our pearls flawless.

LUSTER - is the biggest value factor to pay attention to. Luster measures the rate of reflection (how crisp and detailed it is) on a pearl’s surface, and the amount of light reflected on the pearls.Beautiful luster makes or breaks pearls as a gemstone - pearls without great luster can end up looking like chalky beads. Basically, the brighter, sharper and more reflective a pearl is, the more valuable it will be.

NACRE - is the term used to sum up all the aspects of the crystalline platelets that make up the body of the pearl surrounding the nucleus. It is composed of microns-thin transparent aragonite platelets (themselves made on crystallized calcium carbonate or CaCo3), and densely layered with conchiolin – an organic glue of sorts - in concentric layers around the mother of pearl bead nucleus.

SHAPE - generally the more perfectly round in shape a pearl is, the more rare and prized it is. However many pearl connoisseurs enjoy the unique distinctiveness of baroque pearls. Baroques are off-round, drop and asymmetrical in shape, and are graded according to symmetry.

What Makes Hanadama Pearls So Special?

The term “Hanadama” was coined by the father of cultured pearls himself, Kokichi Mikimoto. He used this term to designate his finest, most beautiful Akoya pearls. “Hanadama” directly translates from Japanese to “Spherical Flower” and are also often called “Flower Pearls” by those in the trade. The delicate shades of pink shimmering over their surfaces are said to be reminiscent of the famous Cherry blossoms that bloom throughout Japan in the Springtime.

Luster and orient. These two attributes, above all others, make a pearl valuable. The brighter and more iridescent a pearl is, the prettier it is. The luster and orient on Japanese Hanadama Akoya pearls is certified to be the very highest and strongest of all Akoya pearls. These attributes are analyzed and certified to meet specific levels set by the Pearl Science Laboratory of Tokyo, Japan. The PSL is the foremost authority on Hanadama pearls, and the only official Hanadama grading lab in the world.

Hanadama Akoya pearls should feature extremely sharp luster – light sources reflected on the surface of the pearl will be very sharp and crisp, with almost no satining or blurring around the edges. You’ll be able to see your detailed reflection smiling back at you when you examine the pearls.

Orient is the iridescent “soap bubble” effect seen only on the finest pearls. White light striking and penetrating the various nacre layers is broken into its spectral rainbow (much like the ‘fire’ in a diamond) and bounced back at the viewer.

These “attributes” are two of the three defining characteristics of Hanadama pearls. The third is nacre thickness. Neither fine luster nor orient would be possible without thickly layered, and tightly compacted crystalline nacre. This is a key element to consider when grading pearls of fine quality.

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