1.70 Ct. Blue Sapphire from Ceylon (Sri Lanka)

This oval shaped blue sapphire weighs 1.70 carat, with exact dimensions of 7.68 by 5.89 by 4.41 millimeters, presenting a transparent body and an intense color intensity. The cutting style is faceted, executed as a mixed brilliant cut, with a well controlled crown and pavilion design that emphasizes both scintillation and color saturation. Clarity has been evaluated at eye level as very slightly included, indicating only minor internal features that do not detract from face up performance, and the stone displays an excellent polish that yields crisp facet junctions and smooth facet planes. The origin of this sapphire is Ceylon Sri Lanka, and the material has undergone responsible heat treatment to enhance color uniformity and minimize silk inclusions, a standard, permanent enhancement within trade practice. The Natural Sapphire Company presents this gem with full transparency on its provenance and treatment history.

From a gemological and lapidary perspective the mixed brilliant cut of this oval is designed to reconcile two key optical goals, brightness and depth of hue. The pavilion angles and facet arrangement were chosen to avoid windowing, by retaining sufficient pavilion depth relative to the mean diameter, producing an effective depth of approximately 65 percent, which favors return of light through the crown while maintaining an even, intense blue across the table. The crown exhibits a traditional brilliant facet layout to promote scintillation under movement, while the pavilion adapts a modified faceting schema to concentrate color return and reduce light leakage. Facet polishing was performed to an excellent standard, producing mirror like facet planes that maximize contrast and optical definition, and careful attention to facet junctions and symmetry ensures predictable light performance in both direct and diffused illumination. The oval outline at 7.68 by 5.89 millimeters makes this sapphire an ideal candidate for fine jewelry applications where both presence and wearability are required.

Geologically this sapphire traces its origins to processes that unfolded over millions of years within Sri Lanka’s complex metamorphic terranes. Corundum crystallized from aluminum rich protoliths subjected to regional metamorphism, where prolonged exposure to elevated temperatures and pressures promoted nucleation and growth of gem quality aluminum oxide. Trace concentrations of iron and titanium substituted within the crystal lattice, producing the blue color through charge transfer and intervalence mechanisms, while minor proportions of other elements influenced tone and saturation. Growth occurred in small pockets and veins within gneissic and marble host rocks, where slow crystallization allowed for well formed crystals with uniform color zoning. Subsequent tectonic uplift and continued weathering liberated many of these crystals from primary host rock, concentrating them in alluvial gravels and river terraces that have long been the source of Sri Lankan gem harvests.

Over geological time the interplay of chemistry, heat and pressure produced a sapphire with both structural integrity and the potential for exceptional optical character. The decision by our cutters to apply a mixed brilliant approach respects the stone’s natural color distribution and inclusion pattern, preserving weight while optimizing optical yield. Heat treatment was applied as a controlled enhancement to stabilize and intensify the blue, improving overall face up appearance without compromising durability or permanence. When set, this 1.70 carat Ceylon sapphire will present as an intense, deep blue oval with balanced brilliance and a refined profile, reflecting both its ancient geological history and the contemporary craftsmanship of The Natural Sapphire Company.