20.90 Ct. Blue Cabochon Sapphire from Ceylon (Sri Lanka)

This exceptional transparent 20.90 carat oval blue sapphire presents a rare combination of size, color and natural origin, attributes that an informed buyer will immediately appreciate. The gem measures 17.91 x 11.27 x 9.36 mm, and its cabochon cut showcases a smooth, domed surface that emphasizes depth of color and a clean, silken luster. Evaluated at eye level the stone carries a clarity grade of very slightly included, a designation that indicates minimal inclusions that do not materially distract from the gem when viewed without magnification. The color intensity is described as intense, a level that creates a rich saturated blue that remains vivid across variable lighting. The polish is excellent, which enhances surface reflectivity and gives the cabochon a luxurious, glass like finish. Importantly this sapphire has received no enhancement, a feature that commands a premium in the marketplace, and its documented origin of Ceylon Sri Lanka places it among the most sought after geographic sources for classic blue sapphire material. At The Natural Sapphire Company we present this gem with full disclosure of these technical attributes so that an educated buyer can assess both beauty and provenance.

From a gemological perspective the attributes of this cabochon are directly relevant to both aesthetic performance and long term value. The very slightly included clarity grade at eye level means that inclusions are present but limited in size and number, and they tend to sit below the dome where they neither interrupt the smooth color flow nor create obvious light leakage. The cabochon cut itself sacrifices the faceted play of scintillation in favor of an even, saturated color field and a strong body color that reads as deep and velvety to the naked eye. Because the polish is excellent the stone exhibits a mirror like surface reflection that outlines highlights clearly while preserving color saturation, a quality that differs from a faceted sapphire where light return and sparkle are dominant. The lack of enhancement, meaning no heat treatment or diffusion has been applied, is increasingly prized by collectors and connoisseurs because untreated Ceylon sapphires retain unaltered natural inclusions and growth structures that are direct evidence of origin and formation. These factors combined make the gem particularly appealing to buyers who prioritize natural state, documented origin, and long term rarity.

Comparing reflective qualities to other gemstones in the same category helps clarify why this piece is distinctive. As corundum, sapphire has a refractive index around 1.76 to 1.77 and a hardness of 9 on the Mohs scale, properties that give it a strong, durable luster and a degree of brilliance when faceted. In its cabochon form, however, the reflective behavior is more about surface sheen and color depth than about internal scintillation. Against faceted Ceylon, Burmese or Kashmir sapphires this cabochon will not sparkle in the same manner, but it will present a more unified, saturated color field that can appear more dramatic in larger sizes. Compared to star sapphires the present stone shows no asterism, so it does not produce a star effect, yet its deep intense color and very slight inclusions often found in cabochon material can offer a more pure blue presence without the milky veil that can accompany strong asterism. When set beside other blue gemstones such as spinel or tanzanite, the sapphire displays a denser, more enduring color under direct and diffuse lighting, and it resists surface wear better over time due to corundum hardness. For the educated buyer seeking a sizable, untreated Ceylon cabochon with excellent polish and a compelling body color, this stone offers a clear value proposition, and at The Natural Sapphire Company we are prepared to provide detailed documentation and personalized advice on setting options that maximize the stone's optical strengths while preserving provenance and long term value.