Diamond polish and symmetry determine a diamond’s quality within the brackets Poor, Fair, Good, Very Good and Excellent. Within GIA reports, both qualities must maintain industry-held measurement standards, and “ideal” stones may be quantified by both these measurements and their hardness.

Diamond Polish


Where polish is considered, many experts believe the quality to be a leading component of diamond excellency. A diamond’s hardness is directly correlated with its luster, and a stone’s polished facets may increase its reflected light.

Princess shape diamond with excellent polish

Princess diamond with excellent polish

Similarly, poorly polished diamond facets may reduce a stone’s reflected light—refracting it away from the diamond’s exterior. Often, professional labs assess a diamond’s polish levels through close examination on a facet-to-facet basis, and resulting in the following appearances:

  • *“Poor” quality diamonds may appear rugged, unclean and very hazy
  • *“Good” quality diamonds may appear unclean
  • *“Excellent” quality diamonds exemplify symmetry, and they appear extremely clear

While polishing has been practiced for generations, even skilled craftsmen often encounter several hardness and grain variations—sometimes making facet cleaning difficult. Sometimes, when this occurs, polish lines appear, revealing a pink color observable with the naked eye.

Diamond Symmetry

Diamond symmetry is related to a diamond’s “preciseness” amongst its various facets. Additionally, symmetry is derived from a diamond’s intersecting and aligned edges. Misshapen, or extra, facets may render tables and cutlets off-center, resulting in wavy girdles.

Asscher shape diamond with excellent symmetry

Asscher diamond with excellent symmetry

Diamonds maintaining poor symmetry may alter the stone’s refraction—misdirecting entered light as it travels throughout the stone. The light may be ejected at wrong angles, reducing the stone’s overall brilliance. Sometimes, diamond cutters grant a stone minor symmetry reductions, so as to bracket a diamond according to brilliance within the nearest category.

Similar to polish, diamond symmetry is rated among Poor, Fair, Good, Very Good and Excellent. Diamonds maintaining Good symmetry, however, aren’t necessarily among a consumer’s first selection for an ideal diamond for several reasons:

  • *A diamond’s symmetry may be purposefully reduced
  • *Most symmetry is achieved through human intervention
  • *Defects produced through Fair symmetry are relatively small

Often, diamonds maintaining Excellent symmetry and polish are priced approximately 10 to 15 percent higher than those within the Good category. Such a premium price is often aligned with a consumer’s “perceived” value. However, where polish and symmetry are compared, polish is notably more valuable than its counterpart.