The pavilion main facets are the large facets that extend from the girdle of a faceted gemstone down to the culet (or to the meeting point of the pavilion mains, where no culet has been polished). In the standard round brilliant cut there are eight pavilion mains, arranged with eight-fold symmetry around the central axis of the stone, and these eight facets are responsible for the majority of the light return that the observer sees through the crown. The pavilion mains, more than any other set of facets in a faceted stone, determine how the stone performs optically — they are the primary reflective surfaces that catch incoming light and turn it back through the crown.

Geometry and symmetry

Each pavilion main in a round brilliant is a kite-shaped four-sided facet, broader at the girdle and narrowing toward the culet. The eight mains meet at the culet (where present) or at a single point, and in fine cutting work they meet within tolerances measured in tens of micrometres. Symmetry across the eight pavilion mains is one of the principal cut-grade considerations: meet-points that fail to align, mains of unequal width or length, and angles that vary between mains all reduce the stone's optical performance and its grade. Symmetry of the pavilion main angles is more consequential for brilliance than symmetry of the lower-girdle facets that fill the spaces between the mains.

Step cuts and fancy shapes

In step-cut stones — emerald cut, asscher, baguette — the pavilion mains are replaced by stepped rectangular facets that descend in concentric levels rather than meeting at a culet. The optical performance of these stones is differently structured: light returns through fewer, larger reflective surfaces, producing the characteristic broad flashes of light return rather than the rapid sparkle of the round brilliant. In fancy brilliant cuts — marquise, oval, pear, princess — the pavilion mains are present but adapted to the stone's outline; the principle of the major facets running from girdle to culet remains, with the count and proportions varying by cut style.

The role of the pavilion mains in extinction and brilliance

The angle of the pavilion mains relative to the girdle plane (the pavilion angle) is the single most consequential measurement in cut grading; this is covered separately under pavilion angle. The pavilion mains' angle determines whether light entering through the crown reflects back to the observer, leaks through the pavilion (windowing), or is internally redirected to leave through facets out of the principal viewing angle (extinction). Where the pavilion mains are correctly proportioned and symmetrically cut, a stone returns light efficiently. Where they are out of proportion or asymmetrically cut, the stone develops the characteristic faults of inferior cut grade.

In the trade

Examination of the pavilion mains under 10x magnification is one of the standard checks on any stone of consequence. The setter and assessor look for: meet-point quality at the culet (whether the eight mains meet at a single point or with visible gaps), symmetry of main width and length around the perimeter, consistent angle (visible as consistent reflection patterns when the stone is rocked under a single light), and absence of cutting faults such as facet polish lines or scratches. Skyjems and other dealers attend to pavilion main symmetry and consistency in the same examination as overall cut grade. See also pavilion, pavilion angle, pavilion depth, lower-girdle facet, crown main.

Further reading

• GIA Gems & Gemology — facet structure and cut grade articles
• International Gem Society — gem cutting reference
• Lotus Gemology — coloured stone cut analysis