Grading Fancy Shape or Fancy Cut Diamonds


What is a Fancy Shaped or Fancy Cut Diamond?

When discussing diamonds, a “fancy shape” is anything other than round. Fancy shapes are cut to to obtain maximum yield from odd shaped rough. While less common than an octahedron, many broken pieces of rough diamond are found. If the lapidary needs to cut an inclusion out of a regular octahedron, an odd shape is also left. These are best cut into fancy shapes, rather than greatly reducing the weight of the finished diamond simply to accommodate a round brilliant design.

Rounds diamonds are easier to cut, since all the facets in a tier are cut to the same angle and depth. They are usually cut on automated machines. On the other hand, fancy shapes must be cut by hand. Since this is extremely time consuming, fancies are primarily found in larger sizes.

Round diamonds have all the facets in a tier cut to the same angle, which is close to the ideal in terms of brilliance and dispersion. Fancy cuts require a variety of angles to get the facets to come together. (If you cut eight symmetrically arranged facets at the same angle, they will come to a point and give you an octagonal outline. In order for the facets to reach the ends of an emerald or other shape, the angles and/or facet arrangement has to change.) As a result of the varying angles, fancies are not as brilliant as rounds.

Fancy cut diamonds have a much broader range of proportions. Length to width ratios are not standardized.  For example, emerald and princess cuts often have tables to 80%, and marquis’ diamonds are so thin that they are significantly less brilliant than other shapes. Fancies cannot be judged by the same standards as rounds. Color and clarity grading the same, but proportion and cut grading varies considerably.

Proportioning

Proportion ranges are much greater for fancies than with rounds. There is no general agreement as to what proportions are best, (as between long or fat pears, stubby or elongated emerald cuts.) Shape appeal counts highly in the proportion grade, but it is difficult to evaluate as there are no standards to go by. It requires a judgment based on your knowledge of diamonds in general and the particular shape you are working with.

Begin your shape analysis by asking three critical questions;

  1. Are corresponding parts evenly made?
  2. How does the chosen cut affect brilliance and dispersion?
  3. Do the chosen proportions add weight that does not contribute to the diamond’s beauty?

The width is equal to 100% for proportioning. For example, a 50% table is 50% of width, not length.

Keep in mind that enlarging the table reduces dispersion. Reducing crown angles also reduces dispersion, and may affect durability in extreme cases. Deep pavilions darken a stone, and a shallow pavilion makes a stone look glassy and therefore less brilliant.

Girdle reflection often visible, hence it is usually faceted.

Proportions from end and side, but mostly face up.

Basic symmetry

Overall attractiveness

LW ratio

Weigh and measure, length width and depth

Emerald, measure length, not diagonal. Hearts to top of lobes, to tip.

Note shape on report. Include familiar trade name, (Princess, marquis,) Split or additonal facets, french tips, etc.

Table Percentage

Measure and record. No general technique for evaluation.

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

Divide width by length.

Crown Angle

Approximate as with rounds. Describe as acceptable, slightly shallow, very shallow, slightly steep, or very steep.

Girdle Thickness

Since faceted, most are thicker than on a round. Pointed tips have thicker girdles to protect them from breakage. The cleft of a heart is also thick, due to cutting technique. These are acceptable.

Judge girdle from all directions. Record average thickness.

Pavilion Depth

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

Hence, the relationship between the depth and brilliance is different than with 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 and others will have excellent brilliance with even deeper pavilions.

Fancies take on a wide variety of shapes. No set rules, must judge by eye. Reflection patterns are not a good judge of pavilion depth.

Must classify as;

  • Acceptable
  • Slightly Shallow
  • Very Shallow
  • Slightly Deep
  • Very Deep

Consider;

  • Face up appearance
  • Total depth percentage
  • Crown height/pavilion depth relationship

Face up;

  • Is the stone reasonably brilliant?
  • If glassy or watery looking, see girdle reflections, probably shallow. If dark, too deep.

Total Depth %

  • Divide depth by width, to .01%. Generally stone between 55% and 65% are OK. Other wise look for thick girdles, thin or thick crowns and pavilions.
  • Determine each, crown, girdle and pavilion.

Crown height/pavilion depth relationship

  • Measure. Visually estimate. Pavilion should be 2.5 to 4.5 times as thick as crown.
  • Together these three will tell you if pavilion is about right, too thick or too thin. Must be taken together.

Bow Tie and Pavilion Bulge

  • Also part of pavilion analysis.
  • Bow tie in brilliants. Face up, many ovals, marquis and pears show a dark shadow resembling a bow tie. Indicates too shallow or too deep. Slightly deep pavilions often eliminate this. Greater the l/w ration, the more pronounced it tends to be.
  • Size and darkness, normal showroom lighting, naked eye. Record findings as slight, noticeable, or obvious.

Bulge in emerald cuts.

  • Ideal pavilion angles 48, 41, and 34. This will create a slight bulge, anything more is excessive.
  • Higher angles save weight but cause light leakage. Does not affect value unless excessive.
  • Judge with loupe from sides and ends. Note if slight, noticeable, or obvious.

**Many graders only record bulge and bow tie on work sheets. Not on customer documents.

Culet Size

  • Judge as you would a round diamond. Base on width only, unless length is distracting and unattractive.

Major Symmetry

  • Should be symmetrical, top to bottom and side to side.
  • Hold with tweezers on table and culet. Look at sides and ends. (Hearts and pears only ends.)
  • Any variations will affect brilliance, plus visual appeal.
  • As with rounds, Major Symmetry (proportions,) or Minor Symmetry, (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, (emerald, oval, marquis,) 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.
  • 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, it is major.
  • Sides not parallel on step cuts. If noticeable without magnification, it is major.
  • Uneven corners on step cuts. Should be equal length. If you can see variation without magnification, it is major.
  • Uneven wings on hearts, pears, and marquis. If you can see variation without magnification, it is major.
  • Uneven lobes on hearts. If you can see variation without magnification, it is major.
  • Uneven shoulders on ovals and pears. If you can see variation without magnification, it is major.
  • Uneven bulge on pavilion of step cuts. Even if not eye visible, major.

Abbreviations

Table off center (T/oc)

Culet off center (C/oc)

Culet Placement on pears and hearts (C Pl)

Keel off center (K/oc)

Out of round outline (OR)

Facet pointing error (Ptg)

Misalignment of crown and pavilion facets (Aln)

Sides not parallel on step cuts (S/P)

Table not a regular octagon (T/oct)

Misshapen facets (Fac)

Table and Girdle not parallel (T/G)

Uneven corners on step cuts (UC)

Uneven wings on marquis, pear, or heart (UW)

Uneven lobes on hearts (UL)

Uneven Shoulders on pears and ovals (US)

Uneven bulge on step cuts (UB)

Wavy Girdle (WG)

Naturals, (which do not affect clarity grade) (N)

Extra Facets, (which do not affect clarity grade)  (EF)

Shape Appeal

More than just symmetrical, should also be graceful and appealing. Look for:

  • Narrow or missing corners on emerald cuts.
  • Wide corners on emerald cuts.
  • High or square shoulders on hearts, pears and ovals.
  • Flat wings on marquis, pear or heart.
  • Bulged wings on marquis, pear or heart.

Note that a marquis that is mounted with prongs on the points will look longer and thinner than if mounted with prongs on sides. More for buying and designing jewelry than  grading.

Undefined points. Many of the above 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.

Narrow or no corners (NC)

Wide corners (WC)

Flat wings (FW)

High Shoulders (HS)

Bulged wings (BW)

Undefined Points (UP)

Mishapped lobes on hearts (ML)

Length to Width Ratio

One of the least influential criteria. Some have more eye appeal than others, may create setting problems or weak tips.

Length divided by width. Written as 1.5:1 and expressed as “one point five to one.” No set rules, but general agreement on proportions.

Emerald Cuts 1.5 to 1.7:1

Hearts 1:1

Triangles 1:1

Marquis 1.75 to 2.25:1

Ovals 1.33 to 1.66:1

Pears 1.50 to 1.75:1

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

Finish

Same as with round stones.

Baguettes

Baguettes are a special case. Usually sold in multiples for accent stones, they have increased value in the matching. Uniformity is essential, as variations are quickly obvious.

Judged on face up appearance. Should be uniform in shape, proportion, and brilliance.

Clarity

Do not over grade inclusions in emerald cuts or ignore small ones in tips of marquis and pears.

Color

May appear uneven. Look in every direction, across width, down length, through sides, etc. Usually best to call color on diagonal. If gem looks darker face up than upside down, lower grade to reflect the color you see. I.E. if H in most directions, but J face up, grade as I.