0.79 Ct. Blue Sapphire from Ceylon (Sri Lanka)

This sapphire is a transparent round stone weighing 0.79 carat, with precise measurements of 5.56 x 5.55 x 3.51 mm. It has been fashioned in a mixed brilliant cut and finished to an excellent polish, graded as eye clean when evaluated at eye level, with vivid color intensity. The material is a natural Ceylon sapphire from Sri Lanka, and it has undergone routine heat treatment to enhance its color and clarity. These objective specifications describe a compact, symmetrical round gem with a balanced depth, consistent dimensions across the girdle, and facet junctions executed to close tolerances, all factors that establish the baseline for predictable optical performance and long term stability in daily wear.

At the material level this sapphire derives its optical behavior from the corundum crystal structure, aluminum oxide arranged in a trigonal lattice, a dense, tightly bonded framework that produces a relatively high refractive index and mechanical hardness of nine on the Mohs scale. The refractive index of corundum, together with low but measurable birefringence, governs how light is refracted and split as it enters the stone. When light passes into the sapphire it is subject to strong internal refraction and multiple internal reflections because of that refractive index contrast with air, and the precision of the cutting determines the angles at which those internal reflections occur. The stone also displays modest dispersion relative to diamond, which means that individual spectral flashes are subtler, but the combination of high refractive index and controlled facet geometry produces bright, concentrated returns of white light, perceived as brilliance, and discrete flashes of color, perceived as scintillation. The crystal lattice also allows for pleochroism in many sapphires, an orientation dependent variation in color, which when allied with a balanced cut can generate lively color dynamics as the stone is viewed from different angles.

The mixed brilliant cut of this round sapphire has been selected to maximize the complementary optical effects of the corundum material. The upper portion uses brilliant style facets to promote a lively pattern of small, intense flashes and scintillation, while the lower portion incorporates step facets to create broader flashes and stable contrast. This combination yields a complex pattern of light return, with the crown facets capturing and redistributing incoming light and the pavilion facets directing that light back through the table. The excellent polish reduces microscopic surface diffusion and preserves the sharpness of facet junctions, permitting unobstructed transmission and reflection of light. Because the stone is eye clean, there are minimal internal interruptions to light paths, which allows the designed facet geometry to operate without scattering from inclusions, and the vivid color intensity provides the necessary chromatic contrast to make the bright returns stand out against saturated body tone. Heat treatment in this instance has improved transparency and color saturation by reducing or altering minute silk and crystallographic irregularities, without changing the fundamental lattice that controls optical properties. As a result of these interrelated factors, the sapphire exhibits a degree of brilliance and scintillation that is difficult to replicate in many other gemstones, a performance characteristic that we document and evaluate at The Natural Sapphire Company, and that makes this 0.79 carat round Ceylon sapphire both visually distinctive and technically well executed for settings intended to highlight its light performance and durability.