1.33 Ct. Cobalt Spinel from Tanzania

This single transparent cobalt spinel weighs 1.33 carat, and measures 7.72 by 5.77 by 3.60 mm, presenting a classic oval outline that balances presence with wearability. The gem displays a dark color intensity, saturated with a deep velvety blue derived from cobalt substitution within the spinel lattice, and it is of Tanzanian origin. The cutting style is a mixed brilliant, combining a brilliant facet arrangement on the crown with controlled pavilion faceting to optimize both scintillation and color delivery. Clarity has been assessed as very very slightly included at eye level, meaning the stone is effectively eye clean, and the polish is excellent, with crisp facet junctions and smooth facet planes that maximize light performance. There has been no enhancement, which preserves the natural optical behavior and stability of the material, and supports long term durability for fine jewelry use.

From a faceting and light performance perspective, the mixed brilliant design for this oval cobalt spinel was selected to reconcile two priorities, intense color saturation and lively brilliance. The proportions yield a pavilion depth that corresponds to an overall depth of approximately 53 percent based on the average of the length and width, a geometry that supports strong return of light without excessive windowing or overt darkness. The crown facet layout has been executed to generate focused flashes of light across the table, while the pavilion facets are oriented to fragment dark tone into lively scintillation, producing a dynamic balance between color and fire. Facet symmetry is closely controlled, which, together with the excellent polish, results in sharp light contrast and clean facet reflections. The very very slightly included clarity grade indicates only minor internal features, likely to be pinpoint or minimally linear in character, which do not interfere with transparency or the visual saturation of the cobalt blue.

In practical jewelry design terms, this 1.33 carat oval cobalt spinel is exceptionally versatile and makes a striking gift for someone special who appreciates technical excellence and natural rarity. Its dark intense blue reads as both modern and timeless when set in platinum or white gold, accentuating cool tone, and it also offers dramatic contrast when mounted in warm yellow gold for a more traditional statement. For rings, a setting that secures the oval with four or six well spaced prongs preserves maximum light entry and showcases the mixed brilliant faceting, while a low profile bezel can be recommended for active wearers seeking additional protection without sacrificing the gem character. As a pendant, the oval format provides a focal point that catches light across a range of environments, from indoor illumination to natural daylight, and the natural unenhanced origin from Tanzania adds provenance and storytelling value to the gift. The combination of natural cobalt induced color, excellent polish, and precise mixed brilliant cutting creates a visual presence that reads as refined and singular, suitable for an anniversary, milestone, or bespoke commission.

At The Natural Gemstone Company we emphasize provenance and technical documentation, and we stand behind the natural, untreated nature of this Tanzanian cobalt spinel. We can provide high resolution imaging, facet orientation details, and additional viewing angles on request to assist in setting design or appraisal. If desired, we will discuss recommended mounting geometries and metal selections to preserve and accentuate the stone characteristics, and we can coordinate with bench jewelers to ensure optimal seat and orientation that maximize color and light performance. For a discerning recipient who values mineralogical authenticity and superior cutting, this cobalt spinel is a memorable and technically impressive gift, combining rare natural color, meticulous craftsmanship, and the assurance of no enhancement, all presented by The Natural Gemstone Company.