Hanadama, Japanese for flower pearl, denotes the pinnacle of Akoya culturing. Unlike AAA or AA+, it is not a grade that a dealer assigns but a laboratory finding. The Pearl Science Laboratory in Tokyo examines each strand individually and issues a numbered certificate.
The requirements are measurable. The nacre layer must be at least 0.4 mm per side, verified by X-ray. The surface may show only minor blemishes, in practice on less than 5 percent of the area. Lustre is measured as a teri value and must be very strong. Added to this is the Aurora effect: under light from below, the pearl must show the rainbow-like play of colour known as orient. A photograph of this forms part of the certificate.
Because only a small fraction of a harvest reaches these values, the price of a Hanadama strand is well above that of an AAA strand of the same size. The other grades are explained in the guide Pearl grades from AAA to GIA.
