Education > Tutorial : Performance / Precision

Tutorial : Precision

All diamonds look nice under bright lights, but most become noticeably average in normal conditions. Those which continue to sparkle and dance have good cut quality. Cut quality can be separated into two distinct areas:

Cut Performance which revolves around light return, and

Cut Precision which can take top performing diamonds to an even higher level.

Micro Cut Precision first became possible in the late 1980s in rounds and is only now surfacing in fancy shapes. This is a measure of how well all of a diamond’s facets align with each other in 3D. It takes improved tools, more time and higher skill sets to accomplish top precision. More importantly it expends more carat weight. When present in top-performing diamonds, cut precision can boost contrast, dispersion, scintillation and overall performance in low-light conditions.

Cut Precision is seen in reflective Optical Symmetry viewers, also known as Hearts & Arrows Viewers. These scopes use a single color and no backlighting to show physical cut alignment. Where other viewers focus only on the crown view, the optical symmetry viewer shows both crown (top) and pavilion (bottom) views.

Important: These are not performance reflectors. They reveal nothing about light return, which is a prerequisite for cut precision to have benefits. Read about the AGS ASET® and Ideal-Scope® in our Performance Tutorial.

How do Optical Symmetry and Hearts & Arrows Viewers work?

The diamond is set face-down to see pavilion cut precision. It is turned over, face-up, to see crown cut precision. When the viewer is placed over the diamond light from above is coded white and light from the sides is coded red (other colors may be used).

When the diamond is cut so exactly that its facet reflections overlap with each other it produces uniform, kaleidoscopic patterns in the viewer. Only a tiny fraction of the world’s diamonds will show crisp, uniform patterns.

Round Brilliant

The Round Brilliant is the only shape with a global nickname for cut precision (“Hearts & Arrows”). The reason for this is obvious when looking through an optical symmetry viewer.

Pavilion: With the diamond upside-down the overlapping reflections create a pattern of eight symmetrical hearts in the pavilion. It takes six perfectly aligned facets to create a single heart. If any facet is off the entire pattern will be distorted.

Crown: Turn the diamond over and you will see eight radiating arrows in the crown. Each arrow is a reflection of two perfectly aligned pavilion mains. The ‘arrows’ are much easier to achieve than the ‘hearts,’ so the hearts view is most important.

Different Shapes have Different Standards

Fancy cuts are not held to the same standards as Round Brilliants. The crisp uniformity of patterns seen in precisely cut rounds is not possible with more complex facet arrangements. As a result shapes other than round are practically never discussed in terms of cut precision. However, as the benefits of cut precision are studied by research labs and made known to consumers we are confident cut-focused manufacturers will begin to pay attention to their development.

Princess Cut

Depending on configuration, a princess cut will have between 24-48 facets on its pavilion and 17-29 cut on the crown. This makes for a wide variety of looks even when the patterns are readable. The princess cut below has a 24 facet pavilion (known as “2-chevron”).

Pavilion: With the diamond upside-down the overlapping reflections create a series of white and red V’s in the pavilion. It takes eight perfectly aligned pavilion facets to create a single V and reflections from other quadrant can impact uniformity. Perfectly symmetrical patterns are rare in diamonds of common sizes (0.50-3.00 cts) but each quadrant can be well-aligned.

Crown: Turn the diamond over and you will see a primary X running through the crown. This is a reflection of four perfectly aligned pavilion mains. A series of symmetrical white reflections indicates alignment of the other crown facets.

Analysis

While the colors do not indicate levels of light return (AGS ASET® and Ideal-Scope® can be used for this) they show how well a diamond’s facets align with each other in 3D. Where other viewers focus only on the crown view, the optical symmetry viewer shows both crown (top) and pavilion (bottom) views.

Round Brilliant Examples in Optical Symmetry Viewer

Princess Examples in Optical Symmetry Viewer

Benefits of Cut Precision

Cut Precision fine-tunes diamonds which already enjoy top performance. The better-defined contrast pattern creates sharper on-off scintillation and more primary colors in dispersion (less pastels and earth tones). Precision cutting maximizes the return of all available light, even in softer lighting conditions. This is a logical result of all of the facets, the tiny mirrors inside the diamond, brought into precise alignment with each other. Face up color is also improved when light gets in and out of a diamond with more intensity. This can be noted in many diamonds with above-average performance. High performance coupled with top cut precision enhances the effect even more.

Why aren’t more diamonds cut like this?

A high level of micro-precision takes modern tools and more time to achieve. It also requires polishing away more carat weight. Assembly-line factories with dated equipment would have to sacrifice more time and produce smaller diamonds to do this, costing millions in time and carat weight.

Interesting Fact: Most consumers are barely aware of how to judge cut quality. As of 2009 only a single digit percentage of the world’s diamonds are even cut for top performance. Far fewer have both top performance and top precision; easily fewer than 1% of all rounds and perhaps 0.01% of princess cuts.

Conclusion

Cut Performance should be a prerequisite for Cut Precision. Understanding that, diamonds which enjoy high performance and precision are dizzying, dazzling and rare treasures to behold.