CUT

What is Cut?

Cut is a word with two meanings.

The first meaning of Cut refers to the Shape of a stone - round, oval, rectangular, marquise, pear, or heart. The second and more important meaning of Cut involves aspects of craftsmanship, including dimensions, angles, symmetry, faceting and polish.

I’ve heard that Cut is the most important of the 4C’s… is this true?

In our opinion, yes. A well Cut diamond is beautiful regardless of its shape, carat weight, color or clarity.

A diamond is the ultimate light-handling machine. A well Cut diamond is a masterpiece of optics designed to return light to its owner’s—or admirer’s eye. To unleash maximum brilliance, fire and sparkle, a diamond must be manufactured with the same expert skill and precision as a fine automobile. This means Cutting is as much the key to diamond performance as engineering is the key to car performance.

Think of diamond buying as, in part, like taking a gem for a test-drive. Just as you base a car purchase on a vehicle’s physical performance, you base your diamond purchase on its visual performance.

Is there a standard diamond Cut?

The most popular and ‘standard’ diamond shape is the round brilliant. The round brilliant is designed to maximize the light performance of a diamond. After years of extensive study, the modern round brilliant has evolved to have a narrow range of acceptable proportions that maximize the optical potential of a diamond and produce the best combination of brilliance, fire and sparkle.

An ‘Ideal Cut’ is the highest standard. A diamond that achieves Excellent ratings in the categories of Light Performance (optical brilliance and optical symmetry), Finish (polish and external symmetry) and Proportions (table size, depth %, crown angle, pavilion angle and girdle thickness) is considered an ‘Ideal Cut’.

How many facets does a diamond have?

It depends on the shape and cutting style. A standard round brilliant has 57 or 58 facets, an emerald step has 49 or 50 facets, a princess has 53 facets, etc.

Some shapes have over 100 facets, but more facets do not necessarily equal more brilliance, it just means that the light is broken up into more rays and reflected in more directions.

Even tiny diamonds, as small as 1-point (0.01ct), are commonly faceted as round brilliants with 57 facets.

What are the different parts of the diamond?

The main parts of a diamond are:

• Table
• Crown
• Girdle
• Pavilion
• Culet

How do I know if a diamond is a good Cut?

The abridged answers…

1. Look and see for yourself. Buy a diamond that you think is beautiful. Buy one that you fall in love with.
2. Ask for a diamond with a GCAL ‘Ideal Cut’ Certificate.
   

Grading every aspect of cut quality falls into two categories - proportions and craftsmanship.

Proportions = Light Return

Diamonds are cut to exact proportions that have evolved over the last hundred years of study. The interrelationship between these proportions—table size, crown angle, pavilion angle, girdle thickness, and culet size—determine how much light that enters the diamond is returned to the observer’s eye in sufficient strength to give the stone full beauty and vitality. This is called light return.

Light return, which is determined by proportions, is described as: Brilliance (the overall brightness and light returned to a viewer’s eye) Fire (dispersive colored light like rainbows from a prism) Scintillation (the sparkle you see when a diamond moves) Because proportions directly influence light return, some people assess cut quality based on proportions alone. They measure parts of the diamond and then either: (1.) determine which grade range the proportions fall within on standard measurement grading charts, or (2.) rely on software to make a digital model of the diamond that tries to predict what the diamond looks like.

Judging cut based on two-dimensional mathematics or theoretical modeling is not the best way to evaluate light performance because it doesn’t take into account slight nuances of faceting, shape, and clarity features.

The best way to judge cut quality is to analyze the actual light return coming from the real diamond. This is how GCAL’s proprietary direct assessment light performance technology works. We photograph the diamond in an environment that clearly distinguishes where light ‘leaks’ out the bottom of the diamond. Then we scientifically calculate the percentage of light leakage versus light return.

On every GCAL certificate, the Optical Brilliance image allows you to see for yourself exactly how much light is coming from the diamond. The dark blue areas are the light leakage and the white areas are the light return.

This is the simplest way to know that your diamond is well cut and has good proportions - no need to worry about numbers, angles and percentages.

Craftsmanship = Symmetry

Craftsmanship is a judgment of the diamond cutter’s workmanship. When a diamond cutter transforms a diamond-in-the-rough into a beautiful gemstone, they first must properly proportion all the angles, and then they must finish each facet with skill, patience and artistry. This is graded as polish and symmetry.

Polish refers to the final finish of each facet. If the diamond’s surface is microscopically smooth and free of scratches then it gets an excellent rating. The more scuffs, the less the rating.

Symmetry is an assessment of each facet’s precise shape, placement, and alignment. Symmetry is graded in two ways:
1. External Symmetry assesses the physical symmetry of each facet and is graded by examining the diamond under 10x magnification.
2. Optical Symmetry assesses the consistency of angles and alignment of facets by looking at the equality of light return. This is graded by placing the diamond in an optical symmetry reader that reveals the patterns of light return. The Optical Symmetry image on every GCAL Certificate is a photograph of the diamond captured while in the optical symmetry reader.

You can see the quality of the cut by looking at the Optical Symmetry image on your GCAL Certificate - the more even the pattern, the better the symmetry. All light returned at the same angles is represented by the same color. For example, red areas represent light being returned within a consistent angle range, green areas represent a different angle range, etc.

Read about How Cut Affects Value