15.76 Ct. Cabochon Moonstone from Ceylon (Sri Lanka)

This 15.76 carat Ceylon moonstone from The Natural Gemstone Company presents as a semi translucent grey oval with dimensions of 18.57 by 15.10 by 8.19 millimeters, a proportion that favors a pronounced domed profile and a broad adularescent sheen. Mineralogically this material is a potassium feldspar in the orthoclase to sanidine series that exhibits a characteristic adularescence produced by thin alternating lamellae of orthoclase and albite, the spacing and uniformity of which govern the quality of the floating light. The medium light color intensity yields a neutral grey body tone that allows the internal sheen to read cleanly across the surface, while the semi translucency provides a soft diffusion of light rather than discrete internal reflections. Origin documented as Ceylon Sri Lanka places this specimen within a tradition of feldspar material known for even lamellar development and stable color, attributes that contribute to predictable optical performance when cut and set in jewelry.

The cabochon cut has been executed to maximize the adularescent effect, with a carefully calibrated dome height of 8.19 millimeters relative to the length and width to create an optimal viewing angle for the float of light. The oval outline is symmetric, the girdle area is smoothly graduated into the dome, and the overall profile demonstrates consistent curvature indicating expert preforming and final shaping. Cabochon orientation was selected so that the lamellar planes run parallel to the base, a standard cutting practice for moonstone that concentrates the adularescent flash across the broad face of the stone rather than dispersing it into multiple weak flashes. The polish is graded excellent, with optical level finish that minimizes surface diffusion and preserves the clarity of the sheen, and the surface exhibits no visible lapping marks or polish haze under typical loupe examination.

Clarity has been evaluated at eye level as very slightly included, a grade that denotes minor, well distributed internal features that do not detract from the overall appearance or the gemological phenomena. These inclusions are subtle, consisting primarily of minute cleavage veils and occasional fine mineral inclusions aligned with the perthitic layering, and they remain inconspicuous against the semi translucent body. Because the adularescence in moonstone is an interference effect, small internal planes and aligned inclusions often integrate into the visual character rather than creating disruptive windows or dead spots. Refractive index for feldspar moonstone typically measures in the range of 1.518 to 1.526, with low birefringence that does not interfere with the single coherent sheen, and specific gravity commonly falls between 2.56 and 2.63. These physical properties confirm expected handling and setting parameters for bench jewelers.

This specimen is offered without any enhancement, a notable point for connoisseurs who prioritize natural material and untreated optical phenomena. The stable body color and intact lamellar structure mean the stone is suitable for a variety of settings that preserve the cabochon profile, with bezel settings and semi bezel settings recommended to protect the perimeter and maintain the dome silhouette. Because of the stone size and dome height, secure mounting and adequate seat depth are important to avoid stress and to allow the adularescence to read without obstruction. Practical care advice includes avoiding ultrasonic cleaning and harsh chemical exposure, preferring warm soapy water and a soft brush for routine maintenance, and storing separately to prevent abrasion to the high polish surface. For buyers seeking documentation or custom mounting, The Natural Gemstone Company can provide additional imagery, measured gemological data, and guidance for design and setting to ensure the stone performs optimally in finished jewelry.