Most people buying a diamond start with carat weight. Then colour. Cut comes last, if at all, because the grade is just a word on a page and nobody explains what it actually means. That ordering is backwards. Cut is the one attribute that makes a diamond look alive — not its size, not its colour grade. A poorly cut stone with a better colour grade will look flat next to a well-cut stone with a lower one. This is not opinion. It is optics.

What Cut Actually Measures

Cut grade is a score for geometry. A diamond cutter starts with rough crystal and makes decisions about where to place the table (the flat top facet), how steep to angle the crown facets above it, and how to angle the pavilion facets below. Each of these angles determines what happens to light when it enters the stone.

Light enters through the table. If the pavilion angles are correct, it bounces off one facet, then another, and exits back through the top toward your eye. That flash is what you see as sparkle. If the angles are too steep or too shallow, light leaks out through the bottom or sides instead. You get a dark, flat stone.

"A colourless diamond with a Poor cut and a faint yellow diamond with an Excellent cut — most buyers, in most lighting conditions, would point to the yellow one as the more beautiful stone."

The Five Grades

IGI Cut Scale for Round Brilliant Diamonds

Grade 01 · Best

Ideal

Table %52–57%
Depth %59–62.3%

Maximum light return. Every facet angle optimised for brilliance.

✦ VAIMA Standard

Grade 02

Excellent

Table %53–58%
Depth %58–64%

Visually indistinguishable from Ideal to the naked eye. Strong choice at any budget.

Grade 03

Very Good

Table %52–66%
Depth %57–67%

Some light leakage. Still performs well. Acceptable if budget requires trade-off.

Grade 04

Good

Table %51–68%
Depth %56–70%

Visible light leakage. Sparkle difference becomes noticeable side-by-side.

Grade 05

Fair

Table %Below 51 or above 70%
Depth %Below 53 or above 74%

Significant light loss. Not recommended for daily wear fine jewellery.

Note on terminology: IGI uses "Ideal" as its top grade. GIA uses "Excellent" at the top and does not use the word Ideal. Both describe the same quality of performance. A GIA Excellent and an IGI Ideal are equivalent.

What You Are Actually Seeing

Three properties determine how a diamond performs in light

Brilliance

White light reflecting back to your eye from inside the stone. What makes a diamond look bright even in low light.

A shallow-cut stone looks grey by comparison — even under the same light source.

Fire

White light splitting into spectral colours as it exits facets at different angles. The tiny colour flashes you see when you tilt a stone.

More visible under warm lighting. What most people describe when they say a stone "dances."

Scintillation

The pattern of light and dark contrasts across the facets as the stone or light moves. What makes a diamond sparkle when you are in motion.

This is what you see on someone's hand as they gesture — that flash-and-catch of ambient light.

All three, brilliance, fire, and scintillation, depend almost entirely on cut. A D-colour stone in a Fair cut will look flat and grey under most indoor lighting. An H-colour stone in an Ideal cut will throw fire across a room. This is the core argument for prioritising cut above the other Cs when you are working within any budget.

Why Indian Buyers Often Compromise on Cut

In most Indian jewellery conversations, carat weight gets discussed first because it is visible and easy to write on a receipt. Colour follows. Cut gets a passing mention — usually just "it's Very Good" — and nobody explains what that trade-off actually costs you in light performance. The result is buyers who spend more on a larger stone with an average cut that underperforms against a smaller, better-cut one sitting beside it.

What to ask any seller: Request the cut grade, the table percentage, and the depth percentage directly from the certificate. All three are printed on every IGI report. They are not trade secrets.

How to Use This When Shopping

Situation 01

Budget under pressure

Hold Ideal or Excellent cut. Reduce carat or accept G/H colour instead.

Dropping cut produces a stone that underperforms its own grade. Dropping colour or carat produces a stone that looks slightly smaller or slightly warmer — differences most people cannot detect in daily wear.

Situation 02

Comparing two stones at similar prices

Choose the higher cut grade, even if the other stone has better colour or clarity.

Colour is often only visible when a stone is face-down. Cut is visible the moment light hits it from any direction. At equivalent prices, a better-cut stone with a slightly lower colour grade will simply look more alive.

Situation 03

Daily wear piece

Ideal or Excellent, non-negotiable.

India's warm LED office lighting is not flattering to poorly cut stones. A well-cut stone performs in all conditions. A badly cut one looks its best under photography lighting — not where you actually live and work.

When you open an IGI certificate, the cut grade appears near the top of the grading section. It is one word. That word is a compression of several precise measurements and should be the first thing you look at, not the last. If it says Ideal or Excellent, the stone's geometry is working in your favour. Everything else follows from there.