Natural pink diamonds are of great value as gems due to their color and rarity. Since synthetic diamonds grown by both HPHT process and CVD method have recently been seen in the gem market, it is crucial that synthetic diamonds be discriminated with high certainty in order to maintain the value of natural stones in the diamond market. In most of natural pink diamonds, birefringence accompanied by high order interference color is observed, which originates from plastic deformation. HPHT-grown synthetic diamond shows characteristic sector zoning which indicates a combination of {100} and {111} faces. In the diamonds studied in the present investigation, the 737nm peak related to Si was detected in PL spectra excited by a 633nm laser; this can be an important indication of CVD-grown synthetic diamond.
