How to Use the Rapaport and Rapnet Diamond Chart

At its simplest level the price list is used by buyers and sellers as a price list of market values for various sizes colors and clarity qualities. There are price guides published by organizations that may well reflect the goings on in local markets. In the international industry and the big end of town, the Rapaport list reigns supreme.

Mr. Rapaport was the first to run a business-to-business electronic diamond price-comparison service. We will help you to understand how it all works, but because professionals use this service there are many complex interpretations and methods that short of you becoming an expert through years of trading, you will never really understand the nuances of this constantly evolving market place.

Let’s consider each of the headings in a price listings search.

Diamond Shape – prices for round brilliants are higher than other cuts. Emerald cuts and heart shapes are generally the least expensive (emerald cut’s yield from rough is usually quite high). Round brilliants have the highest demand and so they turn over faster.

Diamond Size – each weight range has its own price per carat range, however ‘over-sizes’ can attract premiums of 5% to 10%. For instance 0.60ct to 0.69ct range generally cost 10 per cent more per carat than 0.50ct to 0.59ct, even though they are in the same price grid.

Diamond Color and Clarity are self evident, although there are often combinations that are locally hot. For instance the white wave made high color and medium clarity center stone sizes more sought after. Sometimes Rapaport choses not to over react to short term variations, and the result is firmer prices or lower discounts on these goods.

Diamond Prices on a trade sights are not listed in total stone price, only in prices per carat ($/Ct) and % below the list price (Sometimes stones are listed ‘above’ Rap; common for very large stones of say +10ct because the largest listed stones are 5ct.). All fancy shapes are listed against the pear shapes price sheet, even though today the price sheets are published in other shapes as well.

The grading institute or laboratory is listed. Rarely a stone has no certificate and this usually indicates a vendor has pre-listed a stone that has been sent off for grading to a laboratory, this alert’s his customers that this diamond will soon be available. By far the majority of better quality stones have GIA certificates; there is better demand in USA for GIA certs. The grid below shows the common variances in prices from one lab to another, but be warned, comparing certificates is more complex and then you could imagine.

Generally the smallest discounts apply to AGS certificates, but this that does not mean that the market values AGS strictness more highly than GIA grading. Diamond cutters are more likely to send the AGS stones that will make AGS 0 or at least one AGS 1. As long as the GIA have no cut standard they will miss out on this business. But just because the GIA are not given diamonds that falls within the AGS ideal proportions does not mean you should always pay a premium for AGS graded diamonds, because as we have discussed previously many AGS 0’s score quite poorly on HCA.

The most important cut information in Rapaport listings is total Depth% and Table%. The diamond trade has historically believed the quality of diamond cut can be assessed using just these two pieces of information. You know better because you have read the 60:60 section in the tutorial.

Diamond Girdle information is listed in a confusing way because vendors use different nomenclature when they abbreviated the information from the certificates. Girdle has a big impact on a diamonds spread and its value and the industry recognizes this, although it has less impact than it probably should because it is not written in terms that are easily interpreted.

Diamond Culet is generally listed as small to none, and again you will encounter a variety of descriptors. Rarely will you encounter culet large enough to reduce the value of a diamond.

Diamond Polish and Symmetry have a considerable influence on the value of a diamond (see the chart below). This is largely because the terms used are simple and easily understood. Excellent or good, which would most people prefer? The fact is it is usually impossible to tell the difference without a microscope. Because there is so little cut information on diamond certs, consumers jump on any indication of quality, and so these terms have more significant effects on value than they probably should.

Price difference for Round diamonds
1-1.49ct, F-H, VS1-SI2, GIA and AGS
58%-63% Depth, 53%-58% Table

Data for April, 2004
Polish & Symmetry % Price difference
Ex/Ex or Id/Id 0%
Ex/VG -6.5%
VG/VG -8.3%
VG/G -9.8%
G/G -11.6%

Diamond Fluorescence is also listed with a variable abbreviation and as you know blue fluoro reduces the price of high colors and raises the price of lower colors.

Diamond Measurements are listed to within 0.01 mm.

Comments listed on the report are sometimes supplied such as laser drilled, as well as suppliers comment like ‘pair’ AGS 0 (which is an unsubstantiated Sarin or Ogi report), H&A’s, inscription, eye clean etc.


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