12.79 Ct. Cabochon Moonstone from Ceylon (Sri Lanka)

This specimen from The Natural Gemstone Company is a translucent orange moonstone weighing 12.79 carats, cut as a high domed oval cabochon with finished dimensions of 15.28 by 12.48 by 9.13 millimeters. The body color registers as a warm orange with medium color intensity, and the surface exhibits a soft, internal sheen that is characteristic of gem quality moonstone. Clarity has been evaluated at eye level as very slightly included, indicating small internal features that do not materially interrupt the overall visual effect or the play of light. The gem is natural and unenhanced, with no treatments reported, and the documented origin is Ceylon, Sri Lanka, a source renowned for producing moonstones with attractive body color and consistent adularescence.

From a gemological perspective this moonstone is a variety of orthoclase feldspar, and its optical and physical properties are consistent with that species. The refractive index range is approximately 1.518 to 1.526, with very low birefringence on the order of 0.005 to 0.010, which contributes to the stone appearing singly refractive to the unaided eye. Specific gravity for orthoclase is around 2.56 to 2.60, and the Mohs hardness is in the six to six and a half range, indicating moderate resistance to abrasion and a need for protective mounting in rings that will see heavy wear. The defining optical phenomenon for moonstone, adularescence, is present here as a soft, billowing sheen caused by the submicroscopic, lamellar intergrowth of orthoclase and albite. These alternating layers scatter light in a coherent manner, producing the characteristic floating glow, and in this piece the effect is enhanced by the cabochon profile and the translucent bodycolor which allows internal scattering without excessive masking by dark body tones.

The cutting and finishing are executed to emphasize the stone's adularescence and color, rather than to maximize facet brilliance. The oval cabochon has been shaped with careful attention to dome height and symmetry, the crown measuring 9.13 millimeters which represents a relatively high dome in proportion to the stone dimensions. This elevated profile is deliberate, because a higher dome increases the path length of incident light within the laminated structure, producing a broader and more coherent sheen across the surface. The oval outline is well balanced with consistent curvature along the perimeter, and the dome apex is centered, which ensures uniform play of light when the piece is oriented in common mounting positions. The polish is described as excellent, indicating a glassy, mirror like finish achieved through progressive fine abrasives and a final lap with a fine polishing compound. No surface pits, polish lines, or abrasions are apparent under typical loupe inspection, and the reflective highlights photographed on the dome surface confirm the high degree of surface refinement.

Practical considerations for setting, care, and valuation follow directly from the material and cut characteristics. Because the stone is translucent with a warm orange bodycolor, an open back or lightly domed mounting can allow additional light transmission and enhance the internal glow, making pendants and earrings particularly effective showcases. For rings a bezel setting is recommended to provide edge protection to the relatively soft feldspar, and a low profile with secure bezel walls will minimize the risk of chips to the girdle. The substantial depth of 9.13 millimeters means the pavilion does not require extensive undercut in a mounting, but adequate seat support is essential to prevent stress concentrations at the rim. Cleaning should be limited to mild detergent and warm water with a soft brush, avoiding steam, ultrasonic cleaning, prolonged exposure to strong chemicals, and high heat, all of which can compromise the layered structure or induce fracture. In terms of valuation the most important factors are the clean appearance of the dome, the consistency and quality of the adularescence, the medium saturation of the orange bodycolor, the substantial carat weight at 12.79 carats, the excellent polish, the lack of enhancement, and the provenance from Ceylon. Collectors and designers who value the subtle optical phenomena of moonstone will appreciate that this piece combines a strong internal sheen with a warm tone and few eye visible inclusions, making it a versatile center stone for high quality bespoke jewelry.

If you would like further technical data, such as a detailed microscopy report, refractive index readings, or custom mounting recommendations from our lapidary specialists, The Natural Gemstone Company can provide tailored information and ring or pendant mockups based on the exact dimensions and dome profile. We can also advise on complementary accent stones and metal choices that will maximize the visual impact of the orange bodycolor and adularescence while providing appropriate protection for a Mohs six material. This moonstone is presented as a natural, untreated, high dome oval cabochon with precise dimensions and a clarity grade of very slightly included at eye level, and it represents an excellent option for clients seeking a warm toned, luminous feldspar with strong visual character and traditional Ceylon provenance.