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钻石鉴定证书那家最可靠?



       市场上钻石的鉴定证书品种繁多,而且商家都说自己的钻石鉴定证书是最权威的,其实,在利益驱动关系下,几乎所有的证书都有“人情关系”在里面,最好的办法是二条:一是“舍近求远”,二是自己看证书里三个最关键的指标。

       真是无巧不成书。有一次,两个朋友各自拿了0.52克拉、0.53克拉的钻石让我复诊,他们都是在香港买的,净度都是VS1,颜色都是G,持有的都是美国宝石学院出具的GIA钻石证书。我对朋友说:“你们都是我的朋友,我不看你们的石头,你们自己看证书。”然后,我告诉他们,国外钻石鉴定证书,珠宝界公认的主要有“美国的AGS”,这个AGS只出具最完美切工的钻石鉴定证书,拥有这个钻石证书的钻石价格,比同等级的钻石要贵出许多,在国内还很少流通。目前国内珠宝界比较认可的国外证书有“美国宝石学院的GIA”,“比利时钻石高层议会的HRD”,“欧洲宝石学院实验室的EGL”和“比利时宝石学院实验室的IGI”。


   我告诉朋友,看美国GIA钻石证书,关键看三大指标:一是看切工评价。切工评价主要有对称度评价、抛光度评价和总的切工评价,如果三个切工评价都是“EXCELLENT=完美的卓越的”,那么你买的钻石才是最好的。二是看钻石的直径和高度,你们可以用这样的公式计算:直径的三次方×0.00366(允许有±0.03克拉的误差)7 U% W: }* O) R- P7 W- E
     朋友0.52克拉的直径是 5.02毫米,
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也就是说,0.52克拉的钻石直径只有0.46克拉钻石的直径,这样的钻石,珠宝界戏称:烟囱管!这样的“烟囱管”钻石,光都从腰线旁“漏”掉了,这样的钻石占整个钻石市场90%左右呢。 , ~; s. x. Z: t8 U/ z- z; A+ ~1 y: x


     朋友0.53克拉的直径是 5.42毫米,
本部分内容设定了隐藏,需要回复后才能看到
也就是说,0.53克拉的钻石直径竟然达到0.58克拉钻石的直径,比朋友0.52克拉看上去要大许多,但高度却明显低,这样的钻石,珠宝界戏称:飞碟!这样的“飞碟”钻石,光都从底尖旁“漏”掉了,这样的钻石占整个钻石市场5%左右呢。

               不过,国外四大证书,各有特点:

               一、美国宝石学院的GIA,切工评价分类很细,也最严谨.对净度把握也非常准确,弱点是对颜色把握比叫“松”了点。所以,对GIA要“严格把关”的是它的颜色。


              二、 比利时钻石高层议会的HRD,颜色和净度把握都比较精准,惟独对切工评价比较“粗线条”。


            三、欧洲宝石学院实验室的EGL,对净度和切工把握比较准确,惟独对颜色把握太“宽松”了,I色甚至把J色的钻石,定为H色甚至G色的现象发生得太多了,一些犹太钻石商人专门买GIA证书的钻石,然后把GIA钻石证书扔掉,再去出具EGL证书,把I色或J色的钻石,变成H色或G色,然后以比较低的价格出售给贪图便宜的客户。


             四、 比利时宝石学院实验室的IGI钻石证书,对颜色的把握要求太低,给不少惟利是图的钻石商钻了空子。 7 w2 T1 A3 L1 l: V/ G7 F! \


国内钻石鉴定证书,总体来说鉴定的公正性不够稳定。主要有两种倾向:
3 C  |* r! @0 n

         一是“严得离谱”。国内的证书主要有“国家珠宝检测中心”,简称“国检”。比如,一位朋友拿着经过GIA认证为VS1、G的钻石,复检后变成VS1,J色,而更多的现象是G色变成H甚至I色,用这样的“严格”,来确立自己的“权威”,结果把大量钻石商人吓跑了。

          二是“人情证书”是有发生。主要表现在“地方保护主义”,许多消费者把A地买的钻石拿到B地去鉴定,结果造成了许多误会。


          三是对切工评价分类太粗。主要分类是:一般、好、很好。国外证书对钻石切工的7大指标1.台宽比,2.全深比,3,冠角比4、冠高比5、亭深比6、腰厚比,7、底尖比都标示明白,同时对切工的抛光度、对称比都标示的非常详尽,国内证书则太简单化了,不少检测机构连比色石都用锆石代替,误差大也就能理解了。


             切工为什么那么重要呢?当一束白光通过钻石,如果它首先经过钻石的台面进行反射,然后在钻石内部折射,最后完全通过钻石台面折射出去,那么就会把白光分解成七色光,而主要波长的颜色是红、蓝、黄色,所以我们肉眼看一颗很好切工的钻石时,可以感觉到从钻石里发出的七彩光芒,并以红、蓝、黄色光芒为主,转动时可以看到如彩虹一般的光芒。完全折射的光让钻石感觉到非常晶莹透亮,光芒四射,充满魅力。

       而当钻石台面过小,亭深过大时(俗称“烟囱管”),光会在经过一次折射后从另一端的亭部逸出,从而让钻石显得暗淡无光;而钻石台面过大(俗称“飞碟”),亭部过浅,光线未经折射就已经直接从钻石亭部漏出了,当然不会反射出七彩的光芒。

          最理想切工是大部分的光线从台面进后经过内部折射从台面出,最完美的切工就是完全一光不漏的理想反射,只有切工评价全部是“EXCELLENT=完美的卓越的”,您选折的是最苛求的钻石。

          同样一克拉的钻石毛坯,加工成最理想切工的钻石,只能做成0.25-0.30克拉的裸钻,毛坯出成率平均25%左右;如果加工成“烟囱管”或 “飞碟”,则能加工成0.40-0.50克拉的裸钻,所以,切工完美近似苛刻的钻石,你打死钻石商,也不肯太便宜卖给你呢。

Minimum Millimeter Requirements
For Rapaport Specifications A+, A and A–
Sizes 0.30 – 5.00 ct.

Size Range    Min Diameter    Size Range    Min Diameter
0.30-0.34     4.30     3.00-3.09     9.15
0.35-0.39     4.50     3.10-3.19     9.20
0.40-0.44     4.70     3.20-3.29     9.27
0.45-0.49     4.80     3.30-3.39     9.34
0.50-0.54     5.15     3.40-3.49     9.40
0.55-0.59     5.27     3.50-3.59     9.45
0.60-0.64     5.40     3.60-3.69     9.55
0.65-0.69     5.47     3.70-3.79     9.65
0.70-0.74     5.65     3.80-3.89     9.80
0.75-0.79     5.75     3.90-3.99     9.95
0.80-0.84     5.90     4.00-4.09     10.05
0.85-0.89     6.05     4.10-4.19     10.15
0.90-0.94     6.20     4.20-4.29     10.25
0.95-0.99     6.30     4.30-4.39     10.35
1.00-1.09     6.40     4.40-4.49     10.45
1.10-1.19     6.58     4.50-4.59     10.55
1.20-1.24     6.78     4.60-4.69     10.65
1.25-1.29     6.90     4.70-4.79     10.75
1.30-1.39     6.98     4.80-4.89     10.85
1.40-1.49     7.14     4.90-4.99     10.95
1.50-1.59     7.30     5.00-5.09     11.05
1.60-1.69     7.46     5.10-5.19     11.10
1.70-1.79     7.65     5.20-5.29     11.16
1.80-1.89     7.80     5.30-5.39     11.21
1.90-1.99     7.95     5.40-5.49     11.27
2.00-2.09     8.10     5.50-5.59     11.32
2.10-2.19     8.17     5.60-5.69     11.38
2.20-2.29     8.25     5.70-5.79     11.43
2.30-2.39     8.33     5.80-5.89     11.49
2.40-2.49     8.41     5.90-5.99     11.54
2.50-2.59     8.50     6.00     11.60
2.60-2.69     8.63
2.70-2.79     8.76
2.80-2.89     8.90
2.90-2.99     9.02


New Rapaport Diamond Specifications - August 8, 2014


Rapaport is introducing new diamond specifications for a broad range of diamond qualities.
Effective August 8, 2014, The Rapaport Price List will be based on the new “Rapaport Diamond Specification A”.
RapNet the Rapaport Diamond Trading Network will be enabling the characterization and sorting of diamonds based on the new specifications in the near future.
The diamond specifications are subject to change.
Members of the diamond trade are encouraged to comment on the new specifications via email to rapspec@diamonds.net.
RAPAPORT DIAMOND SPECIFICATIONS  -  August 8, 2014
A+AA–
Grading ReportGIAGIAGIA
ShapeRound BrilliantRound BrilliantRound Brilliant
CutExcellentExcellentExcellent
PolishExcellentExcellentExcellent
SymmetryExcellentExcellentExcellent
CuletNoneNoneNone
Depth %59.5 - 62.5%59.0 - 62.5%58.5 - 62.9%
Table %56 - 61%56 - 61%55 - 62%
FluorescenceNoneNone for D-H, IF-VS1,
Faint Blue OK For VS2-I2
Faint Blue Allowed
WeightNo .00 sizesNo .00 sizesNo .00 sizes
GIA CommentsNo GIA Color CommentNo GIA Color CommentNo GIA Color Comment
GIA CommentsNo Knot, Cavity, Naturals
or Extra Facet
No Knot, Cavity
or Naturals
No Knot or Cavity
GIA CommentsNo Graining Comment IF-VS2No Internal Graining Comment
for D-H, IF-VS1
GIA CommentsNo "Grading based on cloud/s
that is/are not shown"
No "Grading based on cloud/s
that is/are not shown"
No "Grading based on cloud/s
that is/are not shown"
Seller RequirementNo tint, black, center
or open inclusions
No Green TintNo Green Tint
Seller RequirementNo Marange DiamondsNo Marange DiamondsNo Marange Diamonds
Minimum MM
for each size
See separate table.See separate table.See separate table.
© Copyright 2014 by Rapaport USA. All rights reserved.
RAPAPORT DIAMOND SPECIFICATIONS  -  August 8, 2014
B+BB–
Grading ReportGIAGIAGIA
ShapeRound BrilliantRound BrilliantRound Brilliant
CutExcellentVG+VG+
PolishVG+VG+VG+
SymmetryVG+VG+VG+
CuletNoneNoneNone
Depth %59.0 - 62.9%58.5 - 62.9%57.5 - 63.5%
Table %55 - 62%55 - 62%55 - 63%
FluorescenceFaint Blue AllowedFaint Blue AllowedFaint Blue Allowed
WeightNo .00 sizesNo .00 sizes
GIA CommentsNo GIA Color CommentNo GIA Color CommentNo GIA Color Comment
GIA CommentsNo Knot or CavityNo Knot or Cavity
GIA CommentsNo Internal Graining Comment
for D-H, IF-VVS
GIA CommentsNo "Grading based on cloud/s
that is/are not shown"
No "Grading based on cloud/s
that is/are not shown"
No "Grading based on cloud/s
that is/are not shown"
Seller RequirementNo Green TintNo Green TintNo Green Tint
Seller RequirementNo Marange DiamondsNo Marange DiamondsNo Marange Diamonds
© Copyright 2014 by Rapaport USA. All rights reserved.
RAPAPORT DIAMOND SPECIFICATIONS  -  August 8, 2014
C+CC–
Grading ReportGIAGIAGIA
ShapeRound BrilliantRound BrilliantRound Brilliant
CutVG+VG+G+
PolishVG+VG+G+
SymmetryVG+VG+G+
CuletNoneNone or SmallNone or Small
Depth %59.0 - 62.9%57.5 - 62.9%
Table %55 - 62%54 - 63%
FluorescenceMedium Blue AllowedStrong Blue AllowedStrong Blue Allowed
WeightNo .00 sizes
GIA CommentsNo GIA Color CommentNo GIA Color Comment
GIA CommentsNo Knot or Cavity
GIA CommentsNo Internal Graining Comment
for D-H, IF-VVS
GIA CommentsNo "Grading based on cloud/s
that is/are not shown"
No "Grading based on cloud/s
that is/are not shown"
Seller RequirementNo Green TintNo Green TintNo Green Tint
Seller RequirementNo Marange DiamondsNo Marange DiamondsNo Marange Diamonds
© Copyright 2014 by Rapaport USA. All rights reserved.



Minimum Millimeter Requirements
For Rapaport Specifications A+, A and A–
Sizes 0.30 – 5.00 ct.
Size RangeMin DiameterSize RangeMin Diameter
0.30-0.344.303.00-3.099.15
0.35-0.394.503.10-3.199.20
0.40-0.444.703.20-3.299.27
0.45-0.494.803.30-3.399.34
0.50-0.545.153.40-3.499.40
0.55-0.595.273.50-3.599.45
0.60-0.645.403.60-3.699.55
0.65-0.695.473.70-3.799.65
0.70-0.745.653.80-3.899.80
0.75-0.795.753.90-3.999.95
0.80-0.845.904.00-4.0910.05
0.85-0.896.054.10-4.1910.15
0.90-0.946.204.20-4.2910.25
0.95-0.996.304.30-4.3910.35
1.00-1.096.404.40-4.4910.45
1.10-1.196.584.50-4.5910.55
1.20-1.246.784.60-4.6910.65
1.25-1.296.904.70-4.7910.75
1.30-1.396.984.80-4.8910.85
1.40-1.497.144.90-4.9910.95
1.50-1.597.305.00-5.0911.05
1.60-1.697.465.10-5.1911.10
1.70-1.797.655.20-5.2911.16
1.80-1.897.805.30-5.3911.21
1.90-1.997.955.40-5.4911.27
2.00-2.098.105.50-5.5911.32
2.10-2.198.175.60-5.6911.38
2.20-2.298.255.70-5.7911.43
2.30-2.398.335.80-5.8911.49
2.40-2.498.415.90-5.9911.54
2.50-2.598.506.0011.60
2.60-2.698.63
2.70-2.798.76
2.80-2.898.90
2.90-2.999.02
© Copyright 2014 by Rapaport USA. All rights reserved.



Below are the historic Rapaport Specifications that are being replaced by the new Rapaport Specifications
Old Specifications as of July 31, 2014
RapaportRapSpec-1RapSpec-2
ShapeRound BrilliantRound Brilliant
Cut GradeExcellentExcellent or Very Good
Polish/SymmetryExcellent or Very GoodExcellent or Very Good
Total Depth %58.6% - 62.9%58.0% - 63.5%
Table %54% - 63%52% - 65%
Girdle ThicknessVery Thin/Thin Medium or Medium-ThickVery Thin-Thick
Cutlet SizeNo large, medium, chip or abradedNo large, medium, chip or abraded
FluorescenceNone or Faint BlueNone or Faint Blue
CommentsNo treatmentsNo treatments
No crown angle commentNo crown angle comment
Size in CaratsMinimum Diameter (mm)Minimum Diameter (mm)
1.00 - 1.096.406.40
1.10 - 1.196.606.55
1.20 - 1.296.806.75
1.30 - 1.397.006.90
1.40 - 1.497.207.10
RapSpec 3Same as RapSpec-2 except medium blue-fluorescence is allowed
NotesRapSpec-1 girdle should not be Very Thin to Thick as this may indicate wavy girdle
RapSpec-1 standards for center or black inclusions, graining and large naturals
will be stricter than RapSpec 2 and 3
© Copyright 2014 by Rapaport USA Inc. All rights reserved. RAPAPORT® is a registered trademark of Rapaport USA Inc.
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