4.69 Ct. Cabochon Moonstone from Ceylon (Sri Lanka)

This 4.69 carat cushion shape blue flash moonstone from Ceylon Sri Lanka measures 9.80 x 9.63 x 6.86 mm, and it has been fashioned as a high domed cabochon to maximize its optical performance. The cabochon profile and cushion outline are the result of deliberate lapidary planning, where the cutter aligns the stone so that the internal lamellar microstructure lies parallel to the base of the dome, creating a broad plane across which light can enter and be modulated. The primary optical phenomenon on display is adularescence, the ethereal blue flash that appears to glide beneath the surface. This effect arises from alternating layers of orthoclase and albite that have exsolved during cooling, forming lamellae whose thickness and spacing are comparable to wavelengths of visible light. Incoming light undergoes multiple internal reflections and constructive interference at these interfaces, producing a coherent, directional sheen rather than discrete facet reflections. The result is a sheen that moves with viewing angle and light source, giving the moonstone a depth and a vitality that is structurally derived rather than surface dependent.

From a clarity and finish perspective this specimen is graded very slightly included at eye level, and it carries a medium light color intensity that supports translucence without overpowering the blue flash. The very slight inclusions are fine to the eye, and in some positions they act as micro lenses that modulate the passage of light through the lamellar planes, occasionally enhancing localized shimmer without creating detracting cloudiness. The excellent polish of the dome is essential, because a smooth convex surface permits maximum transmission and coherent refraction into the lamellar stack. The cutter achieved a balanced dome height of 6.86 mm relative to the 9.80 by 9.63 mm table, which is a proportion chosen to sustain a wide viewing window for adularescence, while maintaining structural integrity and wearability in jewelry settings. No enhancement has been applied to this stone, so the visual characteristics are native to its natural microstructure and original geologic history, and the provenance from Ceylon Sri Lanka is consistent with a tradition of high quality moonstone crystallization and lapidary finishing.

What distinguishes this moonstone from many other gems is the mechanism by which it generates apparent motion and sparkle, a mechanism rooted in layered interference rather than facet geometry. Faceted gemstones produce scintillation and brilliance by redirecting light at polished planes and refractive index contrasts, relying on sharp facet junctions and facet symmetry, whereas this moonstone converts incident light into a diffuse, directional glow that can appear more luminous under soft directional lighting. The cushion cabochon format intentionally amplifies that glow, offering a broad luminous field that designers can orient to show a centered blue flash or an off center streak depending on setting. For practical considerations in mounting and maintenance a bezel setting provides the most secure protection for the high dome and preserves the uninterrupted plane needed for optimal adularescence, while open backed settings can modulate the perceived depth of color and intensity. At The Natural Gemstone Company we document the gem as 4.69 carat, cushion cabochon, 9.80 x 9.63 x 6.86 mm, very slightly included at eye level, medium light color intensity, excellent polish, no enhancement, origin Ceylon Sri Lanka, and we stand behind the natural authenticity and the lapidary standards applied to each piece. For collectors and makers who value the interplay of crystallography and optics this moonstone offers a structurally derived sheen that is both scientifically interesting and visually compelling, a blue flash that results from material physics and cutting strategy rather than from surface tricks, and a tactile presence that translates readily into refined jewelry designs.