The 4Cs of Pink Diamonds

The same four grading terms: Carat, Clarity, Colour and Cut apply to coloured diamonds. However fancy coloured diamonds (FCD’s), are prized and valued based on different interpretations of the 4C’s.

Carat (Weight)

Carat weight has a big impact on pricing, just as it does with colourless diamonds. However, top coloured pink diamonds above one carat (1.00ct) attract a premium, reflecting their rarity in larger sizes. Fancy yellow diamonds, which are often found in very large rough crystals, attract a smaller premium in larger sizes.

Clarity

Clarity refers to the size, placement and visibility of inclusions. Consumers use terms like flaws, which implies the diamond can break. Sadly this is more likely to be true in the case of pink diamonds. Many people are unaware that diamonds can and do break. Argyle pink diamonds often have large surface reaching ‘feathers’ (a polite word for cracks) reducing durability.

However, clarity has less impact on price with Fancy Coloured Diamonds than it does with colourless diamonds. This is partly because it’s the colour you are buying and partly because inclusions are often harder to see in coloured diamonds (and gems).

clarity chart

Clarity Chart

feathers

Holloway Diamonds would refuse to set these two diamonds. Both have a very high probability of breaking during the pressure involved in pressing claws, prongs or bezels over the stones. The cracks that reach the surface are called ‘feathers’ on a grading report. Very often they follow the diamond’s natural cleavage planes and can be extended right through the stone if you bump it.

A couple were suing their jeweller when they lost their expensive Argyle pink; they claimed it was not securely set. They asked me to be an expert witness against the jeweller. From the dimensions on the grading report I found a slightly smaller gem of the same shape to use as a test – it was impossible to get that smaller stone into the setting. As there was no damage to the ring or the claws the only way for the pink diamond to get out was for it to have broken.

imperfect clarity

Although this stone was given an Imperfect clarity grade of I1 by the GIA. We would reject such a stone because the brilliance is reduced by the inclusions. In my opinion, this stone is an I2.

This pear shaped diamond also has an I1 or grade from Gemological Institute of America (GIA). It is not a clarity that we would offer in a colourless diamond at Holloway Diamonds (HD). However, inclusions in coloured diamonds can be harder to see. Pinks very commonly have large inclusions. In the case of this stone, it makes the stone a bit of a bargain because the marks are disseminated throughout the stone and it is ‘eye-clean’ from ‘ring viewing’ distance. The photos are taken with my phone. If I am overseas at a trade fair buying for clients I take photos and a video showing the diamond alongside a calibration stone (example top right). If you want me to buy for you then I will loan you one of those master stones so you can estimate the actual colour from the photos and videos on your screen.

master stones

lucky-I1

The stone in the colour section below is another ‘lucky I1’. The owner who submits a diamond can request a ‘partial cert’ from the GIA, which does not mention the clarity grade. Buyers can take this to mean the stone has a clarity of I1 or lower. In this case the diamond is border line I1 - I2 so the dealer opted to have the clarity grade on the report.

Colour

Argyle pink diamonds made such a big impact on the world of pink diamonds because they often have such striking colour. Bubble Gum, Fairy Floss or Baby Pink are terms used for the most desirable colours. See the diamond in the box below:

The colour in the center is of this stone is ‘bubble gum pink’ - the most desirable from a demand and resale point of view, but not as expensive as a Red colour.

The big difference in colour and appearance between the central table region and the outer crown facets is because of bad cutting. The stone has a very shallow pavilion and an extremely steep crown angle and would be unsaleable if it was a colourless (D to Z) diamond. The ugly colour saturation from crown to table would stop me from buying this diamond. I asked the vendor to send me a 3D file of the diamond as I considered recutting it, but the estimated 30% weight loss would drop it under the magic 1.00ct weight.

bubble gum pink

certificate

 

COLOUR ACCURACY FROM PHOTOS  

Interpreting how diamonds really look from a photo, even if the same vendor took them, is not advisable. Images from different vendors makes it impossible. In this example the first three photos may be consistent because the same set up has been used from the same vendor (though the background variances could mean it was photoshop’ed and the colours may not be comparable). The pear shape is dulled by inclusions. The fourth image is less flattering but probably more realistic. It’s from a manufacturer from whom I buy hundreds of diamonds a year, and these photos do match the stones.

photos

By videoing and photographing prospect stones alongside a calibration stone I have solved this problem and my clients can have me buy on their behalf.

Colour Grading: GIA vs Argyle

The Gemological Institute of America (GIA) is by far the largest global grading organisation and has its own system that it applies to all fancy coloured diamonds. Argyle Diamonds are the major supplier of the worlds’ pink diamonds and they designed their own grading system as they felt the GIA system had shortcomings. People often ask, and expect, that cross referencing is possible. Sadly, it is not so, and no one believes this until they see Argyle / GIA mismatches with their own eyes, let alone the inconsistency within each organisation.

Colour grading is more complex than most assume with three (not two) variables to account for. Graders must evaluate each diamond for hue, tone, and saturation in controlled lighting boxes like that used to judge fabric colours. They are rarely considered to be consistent, but they are the best there is in an imperfect world. You must use these three descriptors to describe colours.

Munsell

 

 

The Munsell colour wheel shows how Hue, Tone and Saturation work together.

Hue  Around the ‘equator’ - a diamond's overall body colour e.g. orangish yellow, yellow, greenish yellow

Tone  Through the ‘centre of the earth’ - A diamond's lightness or darkness

Saturation  The intensity or saturation of colour

A fourth factor is modifying secondary colours, such as a brownish or orangey.

Argyle use PC1, PC2 and PC3 to mean increasingly darker pinkish Brown or pinkish Champagne diamonds. The ‘ish’ refers to the modifying secondary colour. For example, in pinkish Brown or pinkish Champagne, the pink is the modifying colour, with Brown or Champagne the predominant colour; Brownish Pink is more attractive than pinkish Brown.

Before 2009 Argyle used Pink Brown on a scale of 10PB to 1 PB which they later changed to a marketers dream, of PR or Pink Rosé. But the most valuable colours, and what Argyle is most known for, are the purplish Pinks and pure Pinks. Occasionally an Argyle pink is graded as Purple Pink or Pink Purple, meaning the hue is half way between purple and pink. Pinkish Purple diamonds often come from Russia and are not as highly prized, which is strange as pure Purple is very rare and expensive!

Diamond colour graders at the GIA have a tough job of making grade calls for pinks because they are faced with a broader range of colour hues and complex modifiers of orange and brown.

GIA have crazy unpredictable variances in their grades which are evident when you see the diamonds side by side, as shown in the example below.

FIPP

 

These two Pink diamonds are both the same grade - FIpP (Fancy Intense purplish Pink) according to GIA.

In an effort to answer the many questions we receive on matching the two systems, we have taken as much information as we can from diamonds that have been offered for sale with both Argyle and GIA colour grades, and created two charts. One chart is for straight Pink and the other for Purplish Pink. It is possible to do the same for Purple Pink, orangey Pink and brownish Pink, but these two charts will give you the general idea.

Some of the data came from a collector Mr. Ji Wang. As a rule, the darker side of the charts is less desirable than the left hand lighter side. Please do not try to use this as a grading system because it is not that accurate – it is simply to show the very rough correlation.

Generally speaking each lab’s grade sets an underpinning benchmark price for a diamond irrespective of whether the grade given is ‘hard’ or ‘soft’. However, my advice is to buy a diamond that is in strong consumer demand for the cost, one that is desirable at a retail level. This would rule out the majority of Red diamonds because they are often too dark and lacking brilliance or ‘pretty pinkness’. Although many experts will disagree with me on this matter, my belief is that the more potential buyers, the better the chance to resell your diamond and liquidate your investment.

Here is the chart from Argyle (the images have been manipulated by Argyle to demonstrate colour; please do not use these graphics for actual grading with real diamonds):

HD’s best match: Argyle to GIA’s Fancy Pink grades

grading

HD’s best match: Argyle to GIA’s Purplish Pink grades

grade2

 

 

The next chart is from Argyle Diamonds

Argyle Diamonds chart

 

Cut

The Cut of a diamond refers to both its type or shape and its cut quality, which affects its beauty. Fancy coloured diamonds are most often cut into radiant or cushion shapes, as well as pear shapes, ovals and hearts. These cuts are able to bring out and intensify the colour more than round and emerald cuts. The latter cuts cost more as there are fewer of them produced. Also, as the actual colour of the initial rough is usually better, there can be potential for adding value through recutting. Colourless diamonds are valued for brilliance, contrasting sparkles and firey flashes; these factors diminish coloured diamond beauty! What is desirable in colourless stones is not in coloured diamonds.

Below is an exceptional and very expensive emerald cut stone worth around $1 million. Note the Key to Symbols on the report. Whilst clouds often dull a stone, in this case it could ‘smooth’ the colour and make it “pink on pink” and therefore more desirable. As you can see some parts are pale pink and some are deeper and red. Coloured gems like Burmese ruby and Kashmir sapphire with fine silky inclusions are more valuable than crystal clear stones because the body colour of the diamond creates a more even colour. The pale purplish areas result from ray paths that are very short because most of the light has entered the top, bounced off both sides of the bottom or pavilion, and emerged out the top. In the deeper, darker and more saturated areas the ray paths are many times longer because the light is bouncing around inside the stone resulting in more absorption. In general a more even colour is better, but it is rare to achieve this level of colour and beauty in an emerald cut stone. Cushion, oval and radiant type cuts are more commonly used for fancy coloured diamonds (FCD’s) because they have can be cut with longer ray paths all over the stone.

GIA report

 

 

Note the comment on the GIA report mentions inclusions that have not been plotted on the diagram. Lab’s plot only the immediately apparent ‘grade makers’. The ‘Key to Symbols’ are always listed in grade making order. If the feather was first then I would think twice about buying this stone.

DiamCalc Rays

 

Some parts of this stone are deep red, and other parts are pale pink; this is because there are very different ray path lengths in emerald cuts. Above I have modelled an approximation in DiamCalc and ‘shot a ray’ through two different colour zones. The best cutters achieve those longer ray paths across the entire stone, and if this stone (above) was recut (as a radiant) it could potentially be made Red.

On the left the ray marked by the small square in the top image, and the arrow below, is entering the table. Of that light most (66%) will exit via the crown facet on the right. Because the ray path is short you only see a pale facet zone.

The images on the right show light entering at the blue spot (top) directly over one of the saturated red areas. The ray bounces around hundreds of times before all of the light can escape – so we see a much deeper shade because of the much longer ray path.

The dark zones making rectangular patterns are from light that has entered and left from the area obscured by the observer’s head or body, or they are direct leakage out the back of the stone.

 

SPREAD

A very important factor is the apparent “face up” size of a diamond for its weight. GIA and all lab grading reports do not give you this information. I calculate or estimate it using DiamCalc. The number produced compares the surface area of the diamond to an optimum round cut standard of the same weight. Spreads are listed below and colour coded from Excellent to Bad. Most fancy coloured diamonds have poor spreads; it is a key factor in the stones that I reject.

result

 

DARK ZONES

This pear shaped diamond shows a ‘bowtie’ appearance or a dark zone resulting from my black phone being very close to the stone. Dark Zones are caused by the lens or the camera, or by you when you are looking at a gem, the result of light sources being obscured. Test this by poking a small peep hole in a sheet of white paper and looking at any diamond through the hole – all the dark areas will disappear and the diamond can look very washed out and bland.

lucky-I1

The diamond on the far right in the section on Colour above has large whitish inclusions marked as red on the GIA grading diagram, they are feathers (cracks). The big dark areas near the centre are dark zones - an artefact of the cutting and camera lens. Dark zones are undesirable in most fancy coloured diamonds, but are often desirable in colourless diamonds – the dark star you often see in a well cut round diamond create contrast and sparkle. The difference between a stone with very few dark zones, and one where large parts of the stone are dark is as a result of poor cutting. This link shows an example of 44 repolished stones that show both colour improvements and dark zone improvements. It sounds counter intuitive, but the aim in the fancy coloured world is not to create more sparkle, but rather to enhance colour saturation and even-ness.

plotting

5 stones

These five diamonds are roughly in increasing dark zone order. The first orangey stone has very few. The oval has a bow-tie dark zone and some smaller dark areas near the ends with the best colour concentrated in between. The next poorly shaped oval has large unattractive dark zones with evenly distributed colour (and some dust on the surface). The dark zones in this stone are arguably as bad as those in the next two diamonds, but the deeper-darker body colour reduces their negative impact. The radiant cut has poor symmetry because the dark zone on the left is not repeated on the right side. I would not consider the cushion shape on the far right because the dark zones on the pretty body colour are very distracting; they will move across the stone as it is rocked from side to side.

The next section may be interesting if you are considering investing in pink diamonds.