Although the luster of the Pinctada fucata pearls is one of main factors in estimating their quality, the equipment for measuring their luster has not yet been sufficiently developed. Thus, we fabricated a pearl-luster measuring equipment, consisting of a light source, lenses and a charge-coupled-device (CCD line sensor). By using the equipment, the luster
LID of white, yellow, black and green pearls with diameter 8mm were measured. As a result, it was found that there was a fairly strong correlation between
LID and the psy-chological luster of pearls,
LpH; the coefficient of correlation being γ=0.78_??_0.96. The error
ΔL of the luster caused by the deviation from normal pearl-holding-positon was also estimated by computer simulation. The value of
ΔL was found to be relatively small;
ΔL <<10% for deviation of 1.4mm, in the case of the pearl of 8mm diameter.
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