Pavilion — The Lower Half of a Faceted Gemstone
Pavilion — The Lower Half of a Faceted Gemstone
The lower portion of a faceted stone, from girdle to culet, where the angles that determine brilliance and light return are set
The pavilion is the lower portion of a faceted gemstone — the cone- or pyramid-like structure that extends downward from the girdle to the culet. The pavilion is, optically, where the work of brilliance gets done: light entering through the crown is bent on its way through the stone, reflects off the pavilion's angled facets, and is returned through the crown back to the observer. Get the pavilion's angles right and the stone returns light efficiently, with strong sparkle and no visible "window" of leakage; get them wrong and the stone shows extinction (dark zones), windowing (a transparent patch through the stone where light leaks straight out the back), or fish-eye (a circular reflection of the girdle that disrupts the central appearance). The crown can be re-cut without disturbing the optical character of the stone; the pavilion is much harder to modify, and a poor pavilion is the more consequential cutting fault.
Anatomy of the pavilion
In a standard round brilliant cut, the pavilion comprises eight pavilion main facets (the large kite-shaped facets meeting at the culet), sixteen lower-girdle facets (the smaller triangular facets running from the girdle down to the join between adjacent pavilion mains), and an optional culet facet (a small flat polished facet at the bottom of the stone, where the pavilion mains otherwise meet at a point). In step-cut and emerald-cut stones, the pavilion is composed of stepped rectangular facets descending in concentric levels rather than the brilliant configuration. In fancy shapes — marquise, oval, pear, princess — the pavilion adapts to the outline of the stone but retains the main-and-girdle structure of the round brilliant.
Pavilion depth and pavilion angle
Two measurements characterise the pavilion's geometry. Pavilion depth, expressed as a percentage of the stone's girdle diameter, describes how deep the pavilion extends below the girdle. Pavilion angle, measured in degrees, is the angle between the pavilion main facet and the plane of the girdle. The two are related (deeper pavilions imply steeper angles) but are reported separately on grading documents because they capture different aspects of the geometry. Optimal values vary by material: roughly 43 per cent depth and 40.75–41.0° angle for diamond, somewhat shallower for lower-RI materials and somewhat deeper for the higher-RI corundum and chrysoberyl families.
The optical role
Light entering the crown of a stone bends at the air-stone interface (refraction), travels through the stone, encounters the pavilion facets, and either reflects back internally (returning toward the crown) or escapes through the pavilion (light leakage). The angle at which light strikes the pavilion facet relative to the perpendicular determines whether it reflects or escapes; for any given material, there is a critical angle below which total internal reflection occurs and above which light leaks through. The pavilion's angles are set so that light entering through the crown will strike the pavilion below the critical angle on its first or second reflection and return through the crown. Get the angles wrong and the light path either escapes through the pavilion (windowing) or fails to return through the crown's most visible facets (extinction).
In the trade
For dealers and assessors, the pavilion is the most consequential single dimension of cut quality. A stone with strong colour, clean clarity, and good carat weight but a compromised pavilion will read as visibly inferior to a comparable stone with a properly proportioned pavilion. Recutting to repair a defective pavilion is possible but always costs material — typically 10 to 30 per cent of the stone's weight, depending on the magnitude of the correction — and the trade routinely declines to buy fancy-coloured or large-carat material with marginal pavilions because the recut cost-benefit calculation is unfavourable. Skyjems and other dealers attend to pavilion depth percentage, pavilion angle, and visible windowing or extinction in the same examination as crown angle, table percentage, and overall symmetry. See also pavilion angle, pavilion depth, pavilion main, crown.