1.37 Ct. Bluish Green Sapphire from Madagascar

This sapphire is a precisely described specimen from The Natural Sapphire Company, weighing 1.37 carats, fashioned into an elegant oval, and measured at 8.31 by 5.98 by 3.02 millimeters. The cutting style is faceted, executed as a mixed brilliant cut that balances pavilion steps with crown brilliancies to maximize both color and scintillation. Clarity is graded as very slightly included, evaluated at eye level, indicating only minor internal characteristics visible under close inspection, while polish is excellent and the finish shows crisp facet junctions and clean girdle work. Color is intense in saturation, presenting a bluish green hue that shifts subtly with orientation due to pleochroic behavior, and the stone has undergone standard heat treatment to stabilize and enhance this color, consistent with industry practice for material from Madagascar.

To understand the character of this sapphire, consider its deep geological origin. Corundum is aluminum oxide, and its crystallization requires aluminum rich protoliths and environments with low silica activity, conditions typically created during high grade metamorphism or within late stage magmatic bodies. In Madagascar, large tracts of metamorphic basement and localized pegmatitic intrusions provided the chemical and thermal regimes necessary, with the formation process beginning hundreds of millions of years ago during tectonic events that reworked the crust. Under sustained elevated temperature and pressure, aluminum and oxygen reassembled into corundum crystals, while trace impurities such as iron and titanium were incorporated into the lattice, imparting the bluish green color by intervalence charge transfer mechanisms that alter the way the crystal absorbs and transmits visible light.

The optical and physical properties of this gem explain much of its appeal, and are useful metrics for the discerning buyer. Corundum has a refractive index range near 1.762 to 1.770, producing strong internal reflection and a crisp facet return when cut well. Birefringence is modest, approximately 0.008 to 0.010, which can yield subtle doubling of facet edges when viewed with magnification, and contributes to the stone’s visual depth. Specific gravity for corundum is near 4.00, and Mohs hardness is 9, making the sapphire durable for everyday wear in a variety of settings. The bluish green hue observed here arises from a combination of iron and titanium within the crystal, and the stone displays pleochroism, showing more green along one crystallographic axis and more blue along another, a property that the cutter exploited to present a balanced face up color under typical lighting conditions.

The cutter’s decisions are evident in the mixed brilliant design and the proportions of this oval. The average of the length and width is 7.145 millimeters, and the depth of 3.02 millimeters yields a depth to average dimension ratio of approximately 42.3 percent, a relatively shallow profile that emphasizes larger face up presence relative to its weight. This shallower depth was accommodated by the mixed brilliant arrangement, which employs large crown facets for lively scintillation and strategically placed pavilion facets to return light without overly darkening the center. The result is a stone that reads larger on the finger, while maintaining an intense, evenly distributed color and obvious facet contrast when tilted. Excellent polish enhances facet brightness and ensures that light transmission is not muted by surface remnants from the cutting process, and the symmetry of the oval maintains predictable light performance and ease of setting in fine jewelry.

For the buyer who values technical excellence and a documented provenance, this gem presents a compelling combination of natural origin, measured proportions, and skilled lapidary work, available through The Natural Sapphire Company. The heat treatment applied is consistent with established enhancement practices, used to improve hue and clarity stability without compromising the mineral’s integrity, and the very slightly included clarity grade ensures natural character while preserving transparency. When considering a mounting, take into account the pleochroic nature of the stone, orienting the crystal axis to show the preferred balance of blue and green within the chosen lighting environment, and select a setting metal that complements the bluish green hue, with yellow gold providing warm contrast and white metals emphasizing cooler tones. Routine care consists of gentle cleaning with mild detergent and warm water, avoiding harsh chemicals and extreme thermal shocks, which preserves the excellent polish and long term appearance.