11.18 Ct. Cabochon Tanzanite from Tanzania

This listing presents one translucent 11.18 carat round violet tanzanite, dimensions 14.54 x 14.43 x 6.64 millimeters, fashioned as a classic cabochon. The cutting geometry is a high dome round cabochon, executed to emphasize depth and color saturation. Clarity is graded included at eye level, indicating visible internal features when examined without magnification, and the color intensity reads as intense, with a strong saturated violet face up. The polish is excellent across the dome, producing a smooth specular surface. Enhancement is by heat treatment, the standard and stable trade practice that refines brownish tones and amplifies blue violet hues. Origin is Tanzania, and provenance is reflected in the characteristic trichroic response and rich tone. The Natural Gemstone Company presents this piece with its technical attributes documented, suitable for discerning buyers who prioritize optical performance and lapidary provenance.

From an optical and lapidary engineering perspective, the cabochon geometry materially alters how the tanzanite interacts with incident light, compared with faceted cutting styles. The dome height relative to diameter, approximately forty six percent, increases optical path length within the material, producing enhanced subsurface scattering and allowing selective wavelengths to dominate the transmitted and reflected light. Tanzanite has a refractive index in the range of approximately 1.69 to 1.70 and modest birefringence on the order of one one thousandth to one hundredth, combined with pronounced pleochroism along three crystallographic axes. By orienting the stone so that the most desirable pleochroic axis is presented face up prior to capping, the cutter ensures that the dominant face up response is violet rather than brown or green. The convex surface of the cabochon reduces the number of discrete internal reflections seen in a faceted stone, replacing multiple facet return flashes with a softer, more uniform luster. This creates a visual effect in which color saturation appears deeper, highlights are rounded and luminous, and the interplay of internal inclusions and light produces a velvety translucence characteristic of high quality cabochon tanzanite.

Craftsmanship techniques applied to this specimen focus on symmetry of the dome, precise control of curvature, and a mirror quality finish to the polishing stage. The cutter maintained tight tolerances between the declared length and width, producing a near perfectly round outline with minimal deviation, which is critical for even light distribution and predictable color presentation in mounting. The substantial dome height is deliberate, it maximizes color depth and conceals minor surface irregularities, while the excellent polish minimizes surface scattering and permits more light to penetrate the body of the gem before being returned to the viewer. In stones graded included at eye level, internal features become an aesthetic component when managed by cabochon cutting, they can diffuse light to create internal glow, subtle shimmer, or soft zonal contrasts without compromising the overall color intensity. Heat treatment, carried out prior to final cutting, reduces brown absorption bands and stabilizes the blue violet chromophores, enabling the lapidary to orient the stone for an optimal violet face up presentation. For settings, this tanzanite is well suited to closed or semi closed bezels that protect the polished dome, and to designs that benefit from a broad, luminous color field rather than faceted scintillation. The Natural Gemstone Company offers this piece with full technical disclosure and consistent lapidary standards for buyers who value measured optical performance and meticulous finishing.