How to Grade Fancy Cut Diamonds


Summary
“Fancies” — fancy shape or fancy cut diamonds — can have any finished shape other than round. Some well-known examples include princess, marquise, cushion, and oval. Of course, rounds are the most popular diamond cuts, and gemologists can apply standard diamond grading methods to them. However, fancy cut diamonds require different grading criteria.
Reading time: 10 min 38 sec

FI Ryan Colors – cushion

Gemologists can use the same diamond color and clarity grading standards for both rounds and fancies. However, in terms of cut (proportion and finish), fancy cut diamonds differ significantly from standard rounds.

Although the term “fancy” is also used to describe colored diamonds, fancy cut diamonds can be either colorless or fancy colored.

What are the Differences Between Rounds and Fancy Cut Diamonds?

Lapidaries cut fancy shapes to obtain the maximum yield from oddly shaped diamond rough. Although they occur less frequently than octahedrons, many broken pieces of rough are found. In addition, if lapidaries need to cut inclusions of out regular octahedrons, odd shapes may result. Rather than greatly reducing the weight of a finished diamond just to accommodate a round brilliant design, most lapidaries will cut a fancy shape instead.

Faceting Rounds vs Faceting Fancies

All the facets in a tier are cut to the same angle and depth in a round diamond. Thus, rounds are easier to cut compared to fancy shapes. Whereas automated machines usually cut rounds, fancies must be cut by hand. Since this take a lot of time, you’ll usually see fancy cut diamonds in larger sizes than rounds.

How Fancy Cuts Affect Brilliance

Since rounds have all the facets in a tier cut to the same angle, this comes close to the ideal in terms of brilliance and dispersion. In contrast, fancy cuts require a variety of angles to make the facets come together. For example, eight symmetrically arranged facets cut at the same angle will come to a point and give you an octagonal outline. On the other hand, in order for the facets to reach the ends of an emerald-cut or other fancy shape, the angles and/or facet arrangements have to change. As a result of the varying angles, fancies don’t have the brilliance of rounds.

Proportion Analysis for Fancy Cut Diamonds

Fancy cut diamonds have a much broader range of proportions. They don’t have standardized length to width ratios (L/W). For example, emerald and princess cuts often have tables to 80%. Marquise diamonds are so thin they have significantly less brilliance than other shapes. No general agreement exists regarding what proportions work best, even within a particular fancy shape type, such as between long or fat pears, or stubby or elongated emerald cuts.

When you grade proportions in a fancy cut, shape appeal will affect it significantly. Still, evaluation will prove difficult since no standards to go by exist. You must make a judgment based on your knowledge of diamonds in general and the particular shape you’re examining.

Getting Started

Begin by asking three critical questions:

  • Are corresponding parts evenly made?
  • How does the chosen cut affect brilliance and dispersion?
  • Do the chosen proportions add weight that doesn’t contribute to the diamond’s beauty?

Also, remember the following when analyzing fancy cut diamonds:

  • For proportioning, width equals 100%. For example, a 50% table is 50% of width, not length.
  • Enlarged tables reduce dispersion. Reduced crown angles also reduce dispersion and may even affect durability in extreme cases.
  • Deep pavilions darken stones, while shallow pavilions make stones look glassy and therefore less brilliant.
  • Evaluate proportions from end and side, but mostly face up.

Weigh the gem and measure length, width, and depth. For emerald cuts, measure the length, not the diagonal. For hearts, measure the length from the top of the lobes to the tip.

On your grade report, note the diamond’s shape as well as the familiar trade name (for example, princess or marquise). Also, note if the diamond has split or extra facets, French tips, etc.

Table Percentage

There’s no general technique for evaluating the table percentage or table width of fancy cut diamonds. 

Measure point to point opposing belly facets, widest point, even if not aligned. 

Divide width by length and record.

Crown Angle

Approximate crown angles for fancy shapes as with rounds. 

Describe as Acceptable, Slightly Shallow, Very Shallow, Slightly Steep, or Very Steep.

Girdle Thickness

Since girdle reflections are often visible, lapidaries will usually facet the girdles of fancy cut diamond. Thus, they have greater girdle thickness than rounds.

Pointed tips may have thicker girdles to protect them from breakage. Also, the cleft of a heart cut is usually thick due to its cutting technique. Both are acceptable.

Judge the girdle from all directions. Record the average thickness.

Pavilion Depth Percentage

Since fancy shapes aren’t symmetrical all the way around, the pavilion main angles can’t all be the same. The central mains are always at a higher angle than those near the ends. To compensate for these irregularities, lapidaries often cut the central mains at a higher angle than usual. This brings the other facets closer to ideal.

As a result, the relationship between pavilion depth and brilliance in fancy shapes differs from that in rounds. Most fancies will have pavilion depths between 41% and 45%. Due to the extreme variations in fancy shapes, some will have little brilliance in this range, while others will have excellent brilliance with even deeper pavilions.

Fancies take on a wide variety of shapes, so no set rules for evaluating pavilion depth exist. You must judge it by eye. Unlike sight estimates for rounds, reflection patterns are not a good judge of pavilion depth.

Classify pavilion depth as Acceptable, Slightly Shallow, Very Shallow, Slightly Deep, or Very Deep.

Consider the following four elements in your analysis of pavilion depth percentage.

Face-Up Appearance

Is the stone reasonably brilliant?

If the stone looks glassy or watery looking and you see girdle reflections, it’s too probably shallow. If the stone looks dark, it’s probably too deep.

Total Depth Percentage

Divide depth by width, to 0.01%. Generally, stones between 55% and 65% are OK. Otherwise, look for thick girdles and thin or thick crowns and pavilions.

Visually estimate the crown height, girdle thickness, and pavilion depth. The pavilion should be 2.5 to 4.5 times as thick as the crown.

Taken together, these three will tell you if the pavilion is about right, too thick or too thin.

Bowties

When face up, many ovals, marquises, and pears show a dark shadow resembling a bowtie, a type of extinction. This indicates a too shallow or too deep pavilion. Slightly deep pavilions often eliminate this. The greater the L/W ratio, the more pronounced the bowtie effect tends to appear.

Note the size and darkness of any bowties visible to the naked eye in showroom lightning. Record your findings as slight, noticeable, or obvious.

Pavilion Bulge

Emerald cuts may have a pavilion bulge. Ideal pavilion angles of 48°, 41°, and 34° will create a slight bulge. Anything more is excessive.

Higher angles save weight but cause light leakage. Unless excessive, this doesn’t affect value.

Judge any bulge with a loupe from the sides and ends. Note if it’s slight, noticeable, or obvious.

NOTE: Many graders only record bowties and bulges on work sheets, not on customer documents.

Culet Size

Judge culet size as you would for a round diamond. Base the size on width only, unless the length is distracting and unattractive.

Finish Analysis for Fancy Cut Diamonds

For fancy shapes, evaluating basic symmetry involves judging the overall attractiveness of the cut.

Fancy cut diamonds should be symmetrical, top to bottom and side to side. Examine them by holding them with tweezers on the table and culet. Look at their sides and ends. (Hearts and pears only ends).

Any variations will affect brilliance, as well as visual appeal.

Symmetry Errors

As with rounds, major symmetry errors are considered variations in proportion. Minor symmetry errors fall under finish.

  • Off center table. If obvious with loupe, major.
  • Table and girdle not parallel. Should be straight, not wavy. Hearts and pears will be slightly larger at ends. If obvious under 10x, major.
  • Culet or keel off center. Should be centered and straight. From side (for emerald, oval, marquise cuts), ends should taper down at same angle. If one end is steeper than the other, it qualifies as off center. If noticeable under 10x, major. For hearts and pears, culet should be centered on widest part of gem. Too high or too low, when viewed face up, is considered off center. Judge without magnification. If it detracts from appearance, major.
  • Sides not parallel on step cuts. If noticeable without magnification, major.
  • Uneven corners on step cuts. Should be equal length. If you can see variation without magnification, major.
  • Uneven wings on hearts, pears, and marquise. If you can see variation without magnification, major.
  • Uneven lobes on hearts. If you can see variation without magnification, major.
  • Uneven shoulders on ovals and pears. If you can see variation without magnification, major.
  • Uneven bulge on pavilion of step cuts. Even if not eye visible, major.
Abbreviations for Symmetry Terms

Grade the following finish elements under symmetry. Use the following abbreviations on grading reports. (You’ll note rounds and fancies share many of these symmetry terms).

Symmetry Term Abbreviation
Table off center (T/oc)
Culet off center (C/oc)
Keel off center (K/oc)
Out of round outline (OR)
Facet pointing error (Ptg)
Misalignment of crown and pavilion facets (Aln)
Table not a regular octagon (T/oct)
Misshaped facets (Fac)
Table and girdle not parallel (T/G)
Uneven corners on step cuts (UC)
Sides not parallel on step cuts (S/P)
Uneven wings on marquises, pears, and hearts (UW)
Uneven lobes on hearts (UL)
Culet placement on pears and hearts (C Pl)
Uneven shoulders on pears and ovals (US)
Uneven bulge on step cuts (UB)
Wavy girdle (WG)
Naturals (which don’t affect clarity grade) (N)
Extra facets (which don’t affect clarity grade) (EF)

Shape Appeal

Fancy cut diamonds should be more than just symmetrical. They should look graceful and appealing, too.

Look for the following elements that will negatively impact the shape appeal of fancies:

  • Narrow or missing corners on emerald cuts.
  • Wide corners on emerald cuts.
  • High or square shoulders on hearts, pears, and ovals.
  • Flat wings on marquises, pears, and hearts.
  • Bulged wings on marquises, pears, and hearts. (Note that a marquise mounted with prongs on the points will look longer and thinner than if mounted with prongs on the sides. However, this matters more for buying and designing jewelry than grading).
  • Undefined points. Many of the above elements can cause undefined points. Lines should go to a point, not transverse it.
  • Misshapen lobes on hearts. A shallow cleft or broad shoulders make lobes look too wide. If flattish on top, the stone looks squashed.
Abbreviations for Shape Appeal Terms
Shape Appeal Term Abbreviation
Narrow or no corners (NC)
Wide corners (WC)
Flat wings (FW)
High shoulders (HS)
Bulged wings (BW)
Undefined points (UP)
Misshaped lobes on hearts (ML)

Length to Width Ratio

One of the least influential criteria, some L/W ratios have more eye appeal than others. Others may create setting problems or weak tips.

Remember, L/W means “length divided by width.” Write the ratio as “1.5:1,” for example, which reads as “one point five to one.”

Fancy cut diamonds have no set rules for L/W. However, there is some general agreement on their ranges.

Cut L/W Range
Emerald Cuts 1.5 to 1.7:1
Hearts 1:1
Triangles 1:1
Marquises 1.75 to 2.25:1
Ovals 1.33 to 1.66:1
Pears 1.50 to 1.75:1

Determine if the L/W ratio is appropriate and if stone is attractive with eye appeal. Note if the stone is (slightly, noticeably, or obviously) too long or too short. 

Polish

Grade polish for fancy cut diamonds the same as for rounds.

Clarity Grading Fancy Cut Diamonds

Use the clarity grading criteria for round diamonds. 

Don’t over-grade inclusions in emerald cuts or ignore small ones in the tips of marquises and pears.

Color Grading Fancy Cut Diamonds

Use the color grading criteria for colorless or fancy colored diamonds as appropriate.

Color may appear uneven in fancy shapes. Make sure to look in every direction, across width, down length, through sides, etc. Usually, it’s best to call color on the diagonal. If the stone looks darker face up than upside down, lower the grade to reflect the color you see. For example, if you have a colorless fancy that’s H in most directions but J face up, grade it as I.

Notes on Baguettes

Baguettes are a special case. Usually sold in multiples as accent stones, matching increases their value. Since uniformity is essential, variations will obviously stand out

Judge baguettes on the face-up appearance. They should be uniform in shape, proportion, and brilliance.

About the author
Donald Clark, CSM IMG
Donald Clark, CSM founded the International Gem Society in 1998. Donald started in the gem and jewelry industry in 1976. He received his formal gemology training from the Gemological Institute of America (GIA) and the American Society of Gemcutters (ASG). The letters "CSM" after his name stood for Certified Supreme Master Gemcutter, a designation of Wykoff's ASG which has often been referred to as the doctorate of gem cutting. The American Society of Gemcutters only had 54 people reach this level. Along with dozens of articles for leading trade magazines, Donald authored the book "Modern Faceting, the Easy Way."
All articles by this author