0.78 Ct. Blue Sapphire from Tanzania

This gemstone is a transparent 0.78 carat cushion shape blue sapphire, with measurements 5.62 x 4.68 x 2.86 mm, presented as a faceted stone with a mixed brilliant cut. Clarity has been graded as slightly included when evaluated at eye level, and color shows a medium intensity blue that balances saturation and brightness. The polish is excellent, and no enhancement has been applied to the stone. The sapphire originates from Tanzania, and it is offered through The Natural Sapphire Company, where provenance and untreated status are documented as part of our standard practice.

The mixed brilliant cutting style applied to this cushion form combines pavilion facets arranged to encourage internal light return, with a crown facet arrangement that supports strong scintillation and optimal face up presentation. In practice this means the stone exhibits lively flashes of blue and white when moved under light, and the excellent polish ensures minimal light leakage across facet junctions. The medium color intensity is particularly advantageous in a sapphire of this size, because it preserves color saturation without overwhelming the stone with darkness, allowing both color and brilliance to be readily observed in typical lighting conditions. Slight inclusions exist, and they are consistent with natural corundum from primary alluvial and metamorphic sources, however these inclusions do not significantly interfere with the stone s overall transparency or its ability to return light to the eye.

When assessing brilliance relative to more common gemstones, it is important to consider refractive index, dispersion, and cutting. Corundum, the mineral species of sapphire, has a refractive index around 1.76 to 1.78, which is lower than diamond but higher than quartz and many other common gem materials. Diamond s higher refractive index and greater dispersion produce the distinctive rainbow fire that diamonds are known for, but sapphire s combination of refractive index and careful mixed brilliant cutting produces a different and very appealing optical signature. Where diamonds tend to show pronounced fire and scintillation, this blue sapphire delivers a more saturated, focused brilliance, with strong flashes of blue interspersed with white scintillation that emphasize color rather than spectral dispersion. Compared with gemstones such as topaz or amethyst, which have lower refractive indices and typically show less pronounced return of white light and scintillation, this sapphire stands out for its lively facet play and stable color response under varied lighting. Compared with emeralds, which are often more included and more heavily colored, this sapphire offers superior transparency and durability, having a hardness of 9 on the Mohs scale, which makes it well suited for daily wear while maintaining its polished facet integrity.

The combination of untreated origin, mixed brilliant cutting, medium color intensity, and excellent polish make this Tanzanian cushion sapphire a particularly noteworthy example for use in fine jewellery. In a ring setting a slightly elevated open gallery will allow light to enter and maximize the stone s internal reflections, while a bezel set pendant can emphasize the cushion silhouette and protect the girdle. Given the stone s 0.78 carat weight and compact proportions, it is equally appropriate for a solitaire, halo, or a three stone composition where the sapphire s color and scintillation can be accentuated by complementary diamonds or other gemstones. The Natural Sapphire Company provides independent grading information and sourcing details, supporting an informed choice based on clarity, cut, color, and treatment status. This sapphire represents a balance of natural character and optical performance, chosen for its unenhanced state and its capacity to deliver a focused, enduring blue brilliance in wearable jewellery.