Fire
fire | ˈfī(-ə)r
noun
Flashes of different spectrum colors seen in diamonds and other gemstones as the result of dispersion
Fire in a gem stone refers to the sparkle that is influenced by the color of a gem when exposed to light. It is most often used to describe the light refracted by a diamond. It is the counterpart of brilliance, or the colorless light emitted by a gemstone. The cut of a diamond or other gemstone will affect the fire of the stone. The goal of a diamond cut is to achieve ideal proportions that will maximize the brilliance and fire of the stone, so the less brilliant or fiery a gem is, the further away it is from the ideal proportions and can be graded as such. Other factors that can influence fire include the type of light a stone is exposed to, the clarity of the stone, and the cleanliness of the stone.