20.75 Ct. Topaz from Ceylon (Sri Lanka)

This oval shaped blue topaz presented by The Natural Gemstone Company is a technical exemplar, weighing 20.75 carats and measuring 19.98 by 14.94 by 9.15 millimeters, transparent with a vivid color intensity, clarity graded as very very slightly included evaluated at eye level, and finished with an excellent polish, enhancement by irradiation, origin Ceylon Sri Lanka. The proportions of this oval are engineered to preserve mass while supporting optimal optical performance, the length to width ratio yielding a visually pleasing oval outline that concentrates light return toward the table while preserving depth for internal dispersion. The mixed brilliant cut chosen for this piece is intentional, marrying a brilliant style crown with a modified pavilion geometry, and this combination is fundamental to the gem achieving both high brilliance and controlled scintillation. From a trade perspective the datum of 20.75 carats combined with the listed dimensions places this stone in a size category that benefits from careful faceting geometry to avoid windowing while maximizing the appearance of color saturation under a variety of lighting conditions.

The geometric faceting of this mixed brilliant cut blue topaz is configured to maximize light play, with crown facets laid out as a typical brilliant array including star facets, bezel facets, and upper girdle facets, each facet scaled to refine return angles relative to topaz refractive indices. The pavilion architecture is modified from a pure brilliant to reduce leakage through the culet in an oval outline, thereby increasing internal reflections and producing a complex pattern of light and dark areas that animate as the stone moves, creating lively scintillation and a stable field of color. Facet junctions are reported as crisp, and the symmetry is balanced to ensure that optical centers align with the oval axis, which is necessary to prevent optical tilt and to preserve predictable light performance in mounted jewelry. With topaz having a refractive index approximately in the range of 1.61 to 1.64, the faceting angles have been selected to sit near optimal critical angles for internal reflection, this precise geometry enabling the crown facets to refract and disperse incoming light into the pavilion plane where subsequent facet reflections return light toward the viewer, thereby amplifying perceived brightness and depth.

Color behavior in this irradiated Ceylon blue topaz is an integral part of its technical appeal, vivid intensity achieved through controlled enhancement that yields saturated blue tones without significant zoning. The irradiation treatment used on this specimen is industry standard for producing stable blue chromophores in topaz, and subsequent heat protocols can refine hue and saturation, though this particular piece is documented as enhanced by irradiation alone, noting that color stability under normal wear and exposure is consistent with treated topaz of this class. The mixed brilliant faceting intentionally concentrates tone toward the center while permitting lighter pavilion flashes near the girdle, an effect that enhances life in the stone by juxtaposing deep saturated core color with bright peripheral flash, creating the impression of movement and depth. Light transmission is exceptional, the transparency allowing even facet patterns to render with minimal diffusion, and the vivid blue reads consistently from full table face up views to side and crown angles when handled under standard daylight and artificial jewelers lamps.

Clarity and finish are critical for technical buyers and collectors, and this topaz carries a clarity description of very very slightly included at eye level, which in practice means that inclusions are minimal to non distracting when viewed unaided from typical wear positions, and when combined with the precise facet cutting, inclusions do not interrupt the planned light pathways. The excellent polish ensures that facet surfaces act as efficient mirrors, maintaining crisp facet junctions that are necessary for strong scintillation and correct angular light return. Practical mounting considerations include selecting settings that allow light to enter the pavilion and crown unobstructed, such as open basket or prong frameworks, and orienting the stone with its long axis aligned to the intended finger or pendant axis to preserve the engineered light pattern. Routine care for irradiated topaz includes avoiding prolonged exposure to high heat sources above typical jeweler processing temperatures and aggressive chemicals that could affect polish, cleaning with warm soapy water and a soft brush is recommended to maintain optical performance. This specimen from Ceylon combines origin traceability, technical craftsmanship in the mixed brilliant execution, precise dimensions of 19.98 by 14.94 by 9.15 millimeters, and a 20.75 carat weight to present a gem that is both a strong visual presence and a carefully optimized instrument of light, offered by The Natural Gemstone Company for buyers who prioritize geometric faceting and measurable optical quality.