Fire
Fire is the flashes of rainbow colour a diamond disperses as light splits into the spectrum passing through it.
Fire is the flashes of rainbow colour that dart across a diamond as you tilt it. The technical name is dispersion: white light splitting into its spectral colours as it passes through the stone, much as a prism spreads light. Its strength depends heavily on cut, and it is one of the three effects that make a diamond captivating.
How dispersion creates fire
When white light enters a diamond, different wavelengths bend by slightly different amounts. The crown facets act like tiny prisms, spreading that light into reds, greens and blues before it leaves the stone. The steeper crown angles and smaller tables of a well cut diamond generally produce more visible fire, which is why proportion drives the effect.
Fire shows best under focused, single-point lighting, such as spotlights or candlelight, where the coloured flashes stand out. Under soft, diffuse light you see more brilliance than fire. That is why a diamond can look different in a jewellery shop, with its bright spotlights, than at home.
Fire in the cut grade
GIA folds fire into the cut grade alongside brilliance and scintillation. There is a balancing act: proportions that push fire very hard can slightly reduce white brilliance, and the best cuts strike a pleasing balance of both rather than maximising one. This is part of why cut, not colour or carat, decides how lively a diamond looks.
Shape plays a role too. Round brilliants and other brilliant-faceted cuts show strong fire, while step cuts like the emerald produce fewer, broader flashes and lean toward a mirror-like elegance rather than fiery sparkle. If fire is your priority, a brilliant-faceted shape with an excellent cut is the way to get it.
- Fire is dispersion, white light split into spectral colours
- Crown facets act as prisms to create it
- It shows best under focused, point-source lighting
- Brilliant cuts show more fire than step cuts
- Fire is the rainbow colour a diamond disperses from white light.
- It is caused by dispersion, wavelengths bending by different amounts.
- Crown angle and table size strongly affect how much fire shows.
- It appears most under focused, single-point lighting.
- It is part of the GIA cut grade, with brilliance and scintillation.
Fire, in short.
What is fire in a diamond?
Fire is the flashes of rainbow colour a diamond gives off as white light splits into the spectrum passing through it. The technical term is dispersion.
What causes a diamond to have more fire?
Cut and proportions, especially crown angle and table size. A well cut diamond with the right crown geometry disperses more light into visible colour. Brilliant-faceted shapes show more fire than step cuts.
Why does my diamond look more fiery in some lighting?
Fire shows best under focused, point-source light like spotlights or candlelight. Soft, diffuse light brings out brilliance instead, so the same stone can look different at home than in a shop.
Related terms
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