(二)关于净度鉴定的可再现性统计。
在市场上净度为LC级的钻石极少见,大量的是VVS、VS、SI净度的钻石。由于它们都属模糊质量。同一颗钻石关于其净度等级,检验员们仁者见仁,智者见智,常常意见相左。所以要多名检验员协商确定。基本上采用少数服从多数的原则。实际上把净度分级的模糊性掩盖起来。只需将每位检验员的定级意见公布出来。模糊性立即就暴露无遗。
有这样一个实例,表一中每颗钻石的净度都由11名检验员独立作出定级后,再根据少数服从多数来确认等级。类似于唱歌比赛中裁判员们集体打分的制度。虽然用这种办法能最后评出得奖选手的名次。但唱歌水平评定的模糊性是不争的事实。净度也是这样。但消费者很难见到检验员们的分歧的原始资料。所以才会有一种错觉:好像这颗钻石的净度,只能有一个等级。
上面已经证明属于LC与P级净度的钻石,检验员们的意见不会有分歧(除少数情况例外)。 而属VVS、VS、SI级净度的钻石,检验员们的意见总是有分歧(除少数情况例外)。分歧能达到多大程度呢?见表一。
| 净度 人数 编号 | LC | VVS1 | VVS2 | VS1 | VS2 | SI1 | SI2 | P | 级差 | 定级的 可再现率% | ||||
| 0 | 1 | 2 | 3 | 4 | ||||||||||
| 1 | | | | | 3 | 6 | 2 | | | | √ | | | SI1=54.5 |
| 2 | | | | 3 | 4 | 3 | 1 | | | | | √ | | VS2=36.4 |
| 3 | | 2 | 6 | 1 | 1 | 1 | | | | | | | √ | VVS2=54.5 |
| 4 | | | | | | 1 | 9 | 1 | | | √ | | | SI2=81.8 |
| 5 | | 5 | 3 | | | 2 | | | | | | | √ | VVS1=50.0 |
| 6 | | | 4 | 5 | 2 | | | | | | √ | | | VS1=45.5 |
| 7 | | | 3 | 6 | 2 | | | | | | √ | | | VS2=54.5 |
| 8 | | | | 4 | 4 | 3 | | | | | √ | | | VS1或VS2=36.4 |
| 9 | | | 1 | 1 | 6 | 3 | | | | | | √ | | VS2=54.5 |
| 10 | | | | 6 | 4 | 1 | | | | | √ | | | VS1=54.5 |
| 11 | | | | 3 | 6 | 1 | | | | | √ | | | VS2=60.0 |
| 12 | | | | | 4 | 6 | | | | √ | | | | SI1=60.0 |
| 13 | | | 2 | 8 | | 1 | | | | | | √ | | VS1=72.7 |
| 14 | | 8 | 3 | | | | | | | √ | | | | VVS1=72.7 |
| 15 | | 1 | 4 | 6 | | | | | | | √ | | | VS1=54.5 |
| 16 | | 3 | 4 | 4 | | | | | | | √ | | | VVS2或VS1=36.4 |
| 17 | | 2 | 2 | 6 | | | | | | | √ | | | VS1=60.0 |
| 18 | | | | | 1 | 8 | 2 | | | | √ | | | SI1=72.7 |
| 19 | | | 2 | 3 | 6 | | | | | | √ | | | VS2=54.5 |
| 20 | | | | 6 | 4 | | | | | √ | | | | VS1=60.0 |
| 21 | | | | 5 | 4 | 2 | | | | | √ | | | VS1=45.5 |
| 22 | | | | | 4 | 6 | | | | √ | | | | SI1=60.0 |
| 23 | | | | | 1 | 3 | 5 | 1 | | | | √ | | SI2=50.0 |
| 24 | | | 1 | 9 | | 1 | | | | | | √ | | VS1=81.9 |
| 25 | | | | 1 | 2 | 3 | 5 | | | | | √ | | SI2=45.5 |
| 26 | | | | | 3 | 8 | | | | √ | | | | SI1=72.7 |
| 27 | | | | | | 3 | 8 | | | √ | | | | SI2=72.7 |
| 28 | | | 1 | 7 | 2 | | 1 | | | | | | √ | VS1=63.6 |
| 29 | | | 1 | 10 | | | | | | √ | | | | VS1=90.9 |
| 合 计 | 0 | 7 | 13 | 6 | 3 | | ||||||||