Understanding the Brilliance, Fire, and Scintillation of Diamonds

Brilliance is the white light a diamond returns to your eye. Fire is the flashes of rainbow color it makes by splitting light into its spectral colors. Scintillation is the sparkle you see when the diamond, the light or you move. All three depend most on the cut: how well the facets send light back up through the top of the stone.

Here is what each one is, what causes it, and how to judge it in a ring.

Diamond brilliance vs fire vs scintillation at a glance

Diamond fire vs brilliance: what is the difference?

Brilliance is white light; fire is colored light. A diamond with strong brilliance looks bright and lively. A diamond with strong fire throws small flashes of red, orange, green and blue, most visible under spot lighting such as candles or halogen bulbs. A well-cut diamond balances the two.

Why is a diamond brilliant?

Because of the material and the cut together. Diamond has a very high refractive index, about 2.42, so it bends light strongly. When the facets are cut at the right angles, light that enters through the top hits the lower facets and is reflected inside the stone (total internal reflection) instead of leaking out of the bottom. It then leaves through the top, toward your eye. A cut that is too deep or too shallow lets light escape and the diamond looks darker.

What is scintillation in a diamond?

Scintillation is the sparkle in motion: the flashes of light you see as the diamond moves, and the pattern of bright and dark areas across its facets. Some contrast is good; it is what makes a diamond look crisp rather than flat.

How does the cut affect sparkle?

The round brilliant is designed for the most brilliance and fire. Brilliant-style fancy shapes such as the radiant cut, cushion, oval and pear also sparkle strongly. Step cuts such as the emerald cut give fewer, broader flashes, often called a hall-of-mirrors effect, like the Sagitta art deco emerald cut ring. More on shapes: how diamond shape reflects and refracts light.

How do you measure a diamond's fire and brilliance?

For round diamonds, start with the cut grade on the lab report (Excellent or Very Good). For every shape, look at the diamond in more than one light: daylight shows brilliance, spot lighting shows fire, and moving the stone shows scintillation. Light performance viewers can show where a diamond leaks light. More: light performance and the 4Cs.

How to choose a diamond with the most sparkle

• Cut first. It matters more than any other C for sparkle. Choose an excellent or very good cut.
• Clarity: inclusions you cannot see do not dim sparkle. VS2 or SI1 is usually clean to the eye; enhanced clarity stones can look cleaner for the price (see clarity enhanced diamonds).
• Color: near-colorless (G or higher) looks the whitest and brightest.
• Carat: a smaller, well-cut diamond can sparkle more than a larger, poorly cut one.

Do black diamonds sparkle?

Differently. A black diamond is opaque, so it has no brilliance or fire. A well-polished black diamond shines like a dark mirror and flashes along its facets: a quieter light, held in the dark. See our black diamond engagement rings, or pair both kinds of light in black and white diamond rings.

Diamond brilliance, fire and scintillation: FAQ

What is the difference between diamond fire and brilliance?

Brilliance is the white light a diamond returns to your eye. Fire is the flashes of rainbow color made when the diamond splits light into its spectral colors.

What is the brilliance of a diamond due to?

Its high refractive index (about 2.42) and its cut. Light that enters a well-cut diamond bounces off the inner facets (total internal reflection) and leaves through the top.

What is scintillation in a diamond?

The sparkle you see when the diamond, the light or you move: flashes of light and the pattern of light and dark areas across the facets.

Do black diamonds have fire and brilliance?

No. A black diamond is opaque, so light does not travel through it. It shines from its polished surface and flashes along its facets instead.