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Cut Precision
Micro Cut Precision first became possible in the late 1980s in rounds and is only now surfacing in fancy shapes (square, oval, etc.). Cut precision 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. 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. While the colors do not indicate levels of light return (AGS ASET® and Ideal-Scope® are used for this) they show how well a diamond’s facets align with each other in 3D.  Light performance and light return, which is a prerequisite for cut precision to have benefits are viewed using the AGS ASET® and Ideal-Scope®. See our Performance Tutorial for more details.

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).

viewing method

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.
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.

Round Brilliant Examples in Optical Symmetry Viewer
round brilliant precision images


Princess Examples in Optical Symmetry Viewer
princess precision images

 

HRD Diamond High Council of Europe www.Precious-Diamonds.com
McDonnell Diamonds LLC
99 Pine Hill Road #648
Nashua, NH 03063 USA

011 353 1 671 0055 (IRL)
Federation of Jewellery Manufactures of Ireland
 

© McDonnell Diamonds LLC: Some content used with permission.