4.00 Ct. Bluish Green Sapphire from Tanzania

This exquisite transparent 4.00 carat cushion shape bluish green sapphire from Tanzania measures 9.43 x 7.68 x 5.91 millimeters, and it has been expertly faceted in a mixed brilliant cut to maximize both color and light return. With a clarity grade described as very very slightly included at eye level, the stone reads as exceptionally clean to the naked eye, allowing light to travel through the crystal with very little interruption. The vivid color intensity presents a deep, complex teal that shifts subtly between blue and green as the stone moves, and the excellent polish on every facet creates crisp mirror like reflections that enhance its lively scintillation. Because this sapphire is untreated, with no enhancement applied, the tone and saturation are wholly natural, giving a depth and authenticity that is rare among stones of comparable weight and hue.

When evaluating reflective qualities among gemstones in this green to blue green category, sapphire consistently offers a superior balance of brilliance and color saturation. Sapphire, a variety of corundum, has a refractive index around 1.76 to 1.77, which is higher than emerald at about 1.57 to 1.58 and higher than tourmaline at about 1.62 to 1.64, and that higher refractive index translates into stronger light return and more noticeable brilliance under mixed or brilliant faceting. This Tanzanian cushion sapphire benefits from a mixed brilliant cut that leverages corundum s optical properties to produce vibrant facet reflections and controlled contrast, resulting in bright flashes and a pleasing pattern of scintillation when the gem moves. Compared to emeralds, which often exhibit an oily or velvety appearance due to heavy inclusions and lower refractive index, this sapphire reads brighter and cleaner in most lighting, and compared to green tourmalines, which can display a glassy luster with less internal fire, this sapphire shows a firmer, more gem like sparkle. Spinel, which may have a high polish and attractive luster with refractive index near 1.71 to 1.73, can appear lively, yet it lacks the pleochroic nuance and refractive strength that corundum offers in this weight and cut, so a well cut sapphire like this one will often display deeper color and more dynamic reflections than a spinel of similar appearance.

Beyond raw optical numbers, practical factors make this gem stand out on the market. The mixed brilliant pavilion and excellent crown polishing amplify return of light and create a three dimensional depth that is immediately noticeable next to stones of similar color. The very very slightly included clarity ensures the gem remains eye clean while preserving the natural crystal features that confirm its untreated origin, a combination that is uncommon in stones at this carat weight and vivid color. The natural vivid bluish green hue from Tanzania is particularly prized for its balanced tonality that reads equally at home in classic white gold and in warm yellow settings, and because corundum scores nine on the Mohs hardness scale, this sapphire combines aesthetic brilliance with enduring wearability that many softer green gems cannot match. At The Natural Sapphire Company we emphasize full disclosure and responsible sourcing, so you receive not only a beautiful stone, but also confidence in its origin, treatment status, and long term value.

Choosing this cushion shaped Tanzanian sapphire over similar options returns immediate visual and lasting practical rewards. Its mixed brilliant cut outperforms many standard step or simple brilliant cuts for this color category, bringing forth lively contrast and controlled flashes rather than a flat or washed appearance. Its untreated status sets it apart from heat treated or diffusion enhanced stones that may show uniform color at first glance but often lack the natural variation and depth that reveal themselves over time and in varied lighting. The Natural Sapphire Company stands behind this sapphire with expert grading information and recommendations for settings that maximize light entry and face up size, such as open claw or low bezel designs that showcase the pavilion and allow the mixed cut to play with ambient light. For collectors or designers seeking a rare natural teal sapphire that combines exceptional polish, eye clean clarity, strong refractive brilliance, and the reassurance of ethical sourcing, this 4.00 carat cushion from Tanzania offers a compelling, superior choice on the market.