Feb 112012
 

Fair Cut Diamond ReportThis diamond needs some help, serious help!  The diamond is heading out to the cutter, which will be able to correct some of the diamond’s problems.  Here are the specs right now:

Measurements: 7.53 – 7.74 x 4.32
Carat Weight: 1.56
Color Grade: M
Clarity Grade: VS2
Cut Grade: Fair

Polish: Very Good
Symmetry: Fair

Depth: 56.6%
Table: 70%

WOW!

Based on those numbers we can see several problems:

  1. The diamond is not round, the photo shows two points on the edge with dents.  Overall the diamond is just not round.
  2. Depth of 56.6% is much too shallow, normally we like to see round diamonds in the range of 59% – 63%.
  3. Table of 70%, a massive number for a diamond table.  It is rare to find diamonds with such a large table, not salable in today’s market.

When you get a combination of a shallow depth and a large table you get something known as fisheye.  Fisheye appears as a ring under the table facet, it is actually a reflection of the diamond girdle and it is not attractive.  The more the diamond tilts the more the fisheye can be seen.  It is seen above from the 4 o’clock position through the 7 o’clock position as a white area.

To fix this diamond it needs to be made more round and have the table size brought down.  With that recutting the diamond will be quite beautiful.

The problem is the ‘cost’ to have the diamond recut, in terms of weight loss it is going to be expensive.  If we calculate the estimated recut weight based on our diamond recut chart, the end result will probably be in the range of 1.17ct.

The value difference for a 1.55ct vs. a 1.17ct is quite a bit, the good news is I suspect the clarity will probably jump up to VS1…  Off to the cutter, it will take about 6 weeks to get the results back from the GIA about the diamond’s new look so stay tuned for part 2.

Update: The diamond has been returned from the cutter and is now a GIA Excellent cut, see part 2 for an update on this diamond.

Jan 192012
 

I recently did a couple of postings about diamond cut and posted a diamond recut chart that can be used to give an estimate of how much weight would be lost to improve diamond cut.

Lets take a look at a real example on a stone.  When purchased the stone was nice, but a little deep.

Prior to being recut it was 1.15ct so there was room to improve it without going below 1.00ct, which wold be a bad financial move.

Specs Before Recut

Carat: 1.15ct
Measurements: 6.59 – 6.65 x 4.26
Pavilon Depth: 64.4%
Table: 57%
Girdle: Medium – Slightly Thick, polished
Culet: None
Polish: Very Good
Symmetry: Very Good
Cut Grade: Very Good

The cut grade on the above stone would have very good, excellent would not be possible because of the depth being 64.4%.

Off to the cutter it went for a little tune-up.

Specs After Recut

Carat: 1.10ct
Measurements: 6.59 – 6.64 x 4.12
Pavilion Depth: 62.2%
Table: 55%
Girdle: Thin to Medium, Faceted
Culet: Very Small
Polish: Excellent
Symmetry: Very Good
Cut Grade: Excellent

The angle of the pavilion would need to be increased in order to give the stone less depth, resulting in a more impressive stone.  When reducing depth you do not change the diameter of the diamond much.  On this diamond there was no change in the face up size.

The final weight loss was about 4.34%, according to the diamond recut chart we should have lost about 4% going from a depth of 64.4% down to 62.2% so the chart was right on.

Jan 152012
 

Since the GIA released their cut grade system in 2006 people have become obsessed with diamond cut.  Of course there are still plenty of diamonds that were cut before grades were established.

There can be some very interesting cut diamonds out there.  People can sell their diamonds @ http://www.diamonds2cash.com, when we buy diamonds that are badly cut by today’s standards we have to recut them to make them salable.

The following chart can be used to provide a rough estimate of the weight loss required to ‘fix’ a diamond’s cut.   Recutting the diamond is not always so simple, such as if there are large naturals or inclusions but for a quick calculation on the fly, the following data can be used to estimate the final weight of a modern round brilliant diamond.

Diamond Recut Chart

Depth Percentage Deduction Table Percentage Deduction
50.0 – 51.9 22%  43.0 – 45.9  8%
52.0 – 53.9 20%  46.0 – 48.9  6%
54.0 – 54.9  16%  49.0 – 52.9  4%
55.0 – 56.9 12%  53.0 – 53.9  3%
 57.0 – 57.9  8% 54.0 – 54.9 2%
 58.0 – 58.9  6%  55.0 – 56.0 0%
 59.0 – 59.9  4%  56.1 – 58.0  2%
60.0 – 60.9  2%  58.1 – 60.0  3%
 61.0 – 62.0  0%  60.1 – 63.0  4%
 62.1 – 63.0  2%  63.1 – 65.0 6%
 63.1 – 64.0 4%  65.1 – 67.0 8%
64.1 – 65.0 6%  67.1 – 69.0  10%
65.1 – 66.0  8%  69.1 – 73.0  12%
66.1 – 67.0 12%
 67.1 – 68.0 16%
 68.1 – 69.0 18%
69.1 – 70.0  20%

 

Diamonds with a table between 52% – 62% have the potential to fall within GIA’s top cut grade (excellent) but it depends on a number of factors.  Diamonds with a table size outside that range would need to be recut for sure in order to obtain an excellent cut grade.

 

Dec 312011
 

Diamond cut is one of the 4C’s: Cut, Clarity, Color, Carat Weight.

When most people think of diamond cut, they think of shape like round, princess, marquise etc.
At first glance that seems to make sense, but it is not correct.

Diamond cut actually refers to how the facets and angles are put on a diamond. The cut is considered by many as the most important of the 4C’s and has a major impact on the brilliance, fire and overall appearance of the diamond.

Of course what looks best is subjective and there has never (until recently) been a standard
that has been accepted within the industry.

In 1919 a mathematician by the name of Marcel Tolkowsky came up with his idea of what
proportions a diamond should have in order to produce a beautiful diamond. The idea
of cut is to get as much light to enter the diamond, bounce around inside and be returned
back out the top to the viewers eyes. The more light that you can return to the viewer (without leaking out the sides) the more impressive the diamond.

Diamonds being cut within Tolkowky’s ideal range may look nice, but for some reason the industry did not widely accept the range as a standard.

The GIA which is recognized as one of the leaders in diamond grading, research and education
embarked on the massive task of coming up with a cut grade system. Obviously their desire
would be to get their system accepted by the industry.

They spent more than 10 years researching diamond cut, finally updating their reports with the addition of a cut grade (for round diamonds only) in 2006. They do not use the term ideal cut, rather they released a fairly simple scale which goes from Excellent to Poor.

  • Excellent
  • Very Good
  • Good
  • Fair
  • Poor

Their cut grade was immediately accepted by the industry, they license the technology to

other diamond labs and hardware manufactures such as Sarin and OGI Systems.

Prior to the GIA’s standard diamond cutters would essentially cut a diamond as they
wished, often to retain as much weight of the rough diamond as they could rather than
cut the diamond to make it perform as well as it could. Diamonds are sold by weight
so it was to their advantage to keep as much of the weight as possible.

The GIA cut grade system makes it easy to pick a diamond based on the cut grade which is clearly stated on the diamond report. The difference in appearance between a diamond that has the grade excellent vs. good can be quite amazing.

As a general rule of thumb, if you are buying a round diamond you want to purchase the
highest cut grade you can afford. The price difference between a poor cut and excellent
cut diamond is massive and so is the visual appearance.

The good news is there are very few diamonds entering the market that are have cut grades below Very Good.  Diamond buyers made their choices known, they want a quality cut diamond and diamond cutters now cut largely based on the GIA cut grade scale.