The Barion cut is a patented mixed-cut design developed by South African master cutter Basil Watermeyer and first described in 1971. It combines a step-cut crown — typically square or rectangular in outline with cropped corners — with a brilliant-cut pavilion distinguished by a set of distinctive half-moon, or lunette, facets that radiate symmetrically from the culet toward the girdle. This architectural marriage of two historically separate cutting philosophies allows the Barion to achieve levels of brilliance and scintillation that a pure step cut cannot, while retaining the broad, open table and clean geometric lines that step-cut devotees prize. The design has been particularly influential in the cutting of coloured gemstones, where the management of light return and colour saturation are often competing demands.

Origins and the Patent

Basil Watermeyer, working in Johannesburg, registered the Barion cut as a formal patent in 1971. The name is a portmanteau of Barry — the name of his wife — and his own surname, a personal attribution that is well documented in gemmological literature. Watermeyer's central insight was that the pavilion of a gemstone, not the crown, is the primary engine of brilliance: light entering through the table must be totally internally reflected by the pavilion facets and returned to the eye. A conventional step-cut pavilion, with its parallel rows of elongated rectangular facets, is relatively inefficient at this task. By replacing those facets with a brilliant-style arrangement anchored by the characteristic half-moon elements, Watermeyer dramatically improved the optical performance of rectangular and square stones without abandoning the step-cut crown geometry that gives such stones their distinctive, architectural character.

The original Barion patent described a square or near-square outline with four cropped corners — a form sometimes called a cushion square in the trade — though rectangular Barion proportions were also specified. The cropped corners serve a dual purpose: they reduce the mechanical vulnerability of sharp corners to chipping, and they introduce additional facet planes that contribute to the stone's overall light return.

Facet Architecture

The defining structural feature of the Barion cut is the half-moon pavilion facets. In a standard brilliant cut, the pavilion is divided into main facets and lower girdle facets arranged in a radiating pattern around the culet. In the Barion, this arrangement is modified so that large, curved or angled lunette facets sweep from the culet region toward the mid-girdle, creating a visual effect sometimes described as a cross or star when the stone is viewed through the table. This pattern is responsible for both the cut's superior light-handling and its immediately recognisable appearance under magnification.

A fully faceted Barion in its classic square form typically carries:

• A step-cut crown with a large table facet, four corner facets, and rows of step facets parallel to the girdle edges.
• A brilliant-style pavilion incorporating the signature half-moon facets, main pavilion facets, and lower girdle facets arranged to maximise total internal reflection.
• A small culet, either pointed or very slightly truncated, consistent with modern precision cutting.

The precise facet count varies with the outline and the cutter's interpretation of the patent, but the half-moon pavilion elements remain the non-negotiable diagnostic feature.

Optical Advantages and the Bow-Tie Problem

Rectangular and elongated brilliant cuts — including the oval, marquise, and pear — are susceptible to the bow-tie effect: a dark, butterfly-shaped shadow that appears across the width of the stone when it is viewed face-up. This shadow arises because light striking the central pavilion facets at certain angles is directed away from the observer rather than returned through the table. The Barion's pavilion geometry, by distributing facet angles more evenly across the stone's footprint, substantially reduces this phenomenon. For coloured gemstones in particular, where a bow-tie can create an unattractive dark zone that competes with the stone's body colour, this is a meaningful practical advantage.

The mixed-cut approach also allows the lapidary to tune the balance between brilliance and colour saturation. A deeper pavilion angle intensifies colour by increasing the optical path length through the stone; the Barion's brilliant pavilion can be cut to exploit this while the step-cut crown preserves the broad colour windows that make coloured stones visually compelling from a distance.

Influence on Subsequent Cuts

The Barion cut's influence on the development of square and rectangular fancy cuts in the latter decades of the twentieth century was considerable. Two cuts in particular are directly descended from or closely related to Watermeyer's original design:

• The Quadrillion (also known as the Squarillion), developed in the 1980s, adapts the Barion concept to a strict square outline without cropped corners, with a fully brilliant-style pavilion and a modified crown. It was marketed primarily for diamonds.
• The Princess cut, which became the dominant square fancy cut in the diamond trade from the 1980s onward, shares the Barion's mixed-cut philosophy — step or chevron crown, brilliant pavilion — though its precise facet arrangement differs and its development involved multiple cutters and patent claims. The princess cut's commercial success owes an intellectual debt to the Barion's demonstration that a square stone could achieve round-brilliant levels of fire.

The Barion name itself is used more commonly in the coloured-gemstone trade than in the diamond trade, where the princess cut has largely supplanted it in popular terminology, even when the underlying facet architecture is closely related.

Applications in Coloured Gemstones

The Barion cut is particularly well suited to coloured gemstones for several reasons. Many fine coloured rough crystals — sapphire, tanzanite, tourmaline, spessartine garnet — occur in tabular or prismatic forms that yield well to a square or rectangular outline, minimising waste. The step-cut crown's broad table and clean facet planes display the stone's body colour with clarity and depth, while the brilliant pavilion ensures that the stone does not appear lifeless or windowed — a common failing of poorly cut step-cut coloured stones where light passes straight through the pavilion without reflection.

Cutters working with strongly pleochroic materials such as tanzanite or iolite may orient the rough so that the Barion's large table facet presents the most desirable pleochroic colour to the viewer, while the pavilion's light-scattering properties blend the secondary colours into the overall appearance rather than allowing them to dominate in an unflattering way.

In the trade, a well-executed Barion in a fine tanzanite or sapphire is regarded as evidence of skilled, considered cutting rather than weight-retention cutting — a distinction that increasingly commands a premium as the market for precision-cut coloured stones matures.

Identification and Grading Considerations

Identifying a true Barion cut, as opposed to a generic square mixed cut, requires examination of the pavilion under magnification. The half-moon facets radiating from the culet are the definitive diagnostic feature; without them, a stone may be described as a square mixed cut or a modified cushion, but not properly as a Barion. Gemmological laboratories do not typically issue cut-grade reports for coloured gemstones in the way they do for diamonds, so the designation relies on the cutter's own documentation or on the examiner's direct observation of the facet pattern.

There is no universally standardised Barion proportion system equivalent to the GIA's diamond cut-grading parameters. Cutters adapt the proportions — table size, crown height, pavilion depth, girdle thickness — to the optical properties of the specific material being cut, which means that Barion cuts in sapphire, tanzanite, and tourmaline may differ substantially in their exact angles while sharing the same fundamental facet architecture.

Further Reading

• GIA Gems & Gemology — archive of cutting and faceting research
• International Gem Society — Mixed Cuts