15.47 Ct. Cabochon Tanzanite from Tanzania

This offering from The Natural Gemstone Company is a single, substantial tanzanite weighing 15.47 carats, presented in a round cabochon shape, with precise dimensions of 12.45 by 12.38 by 10.63 mm. The stone is translucent with an intense violet color intensity and an excellent polish that produces a pleasing, even luster across the domed surface. Clarity has been graded as included at eye level, which means internal features are visible to the unaided eye but do not undermine the gem's overall appeal when viewed as a finished cabochon. The piece originates from Tanzania, and the material has undergone standard heat treatment to enhance its blue to violet tones, a widely accepted practice within the trade that improves color without compromising stability when handled properly. The cabochon cut has been selected to best display the evenly saturated violet hue and to present a smooth, continuous surface for jewelry applications that favor color and translucency over faceted brilliance.

From a gemological perspective this tanzanite displays the hallmarks collectors and knowledgeable buyers seek in a high quality cabochon specimen. Tanzanite is a variety of zoisite and is known for strong trichroism, which in faceted material can show distinct bluish, violet and burgundy flashes depending on orientation. In this cabochon format the trichroic character contributes to depth of color and internal vibrancy rather than distinct color flashes, and the heat treatment applied has reduced brownish zoning that would otherwise mute the vivid violet. The included clarity grade indicates natural internal features such as fine crystals, needles, or slight veils, typical of material from the Merelani mining region in Tanzania, and these inclusions provide a natural fingerprint that attests to the stone's authenticity and provenance. The excellent polish minimizes surface distortion and maximizes the even play of light on the dome, and the sizeable 15.47 carat weight gives this gem an important presence for collectors, designers and investors who value rarity and provenance.

When assessing durability it is important to set expectations for daily wear and for mounting options. Tanzanite typically registers between 6 and 7 on the Mohs scale of mineral hardness, which places it below corundum varieties such as sapphire and ruby, which are a 9, and below diamond which is a 10, while it is similar to or slightly softer than quartz which rates a 7. This means that tanzanite will be more susceptible to abrasion and scratching than harder gem materials, and it also exhibits a distinct cleavage which can make it vulnerable to sharp blows or hard knocks. For these reasons we recommend protective settings such as bezels or halo style mounts that shelter the girdle and pavilion, or using this cabochon in pendants or earrings where the risk of impact is lower than in daily wear rings. Routine care should be gentle, consisting of warm soapy water and a soft brush, avoiding steam cleaning and ultrasonic cleaners especially for included stones, and avoiding exposure to harsh chemicals and sudden thermal shock. The fact that the piece has been heat treated is an industry standard, and this treatment is stable under normal wearing and cleaning conditions when proper care guidelines are followed.

For the educated buyer this tanzanite offers a compelling combination of size, color intensity, provenance and collectible value. Large tanzanites over 10 carats, and in particular those with intense violet saturation, are uncommon because of the limited geographic source of tanzanite, which is restricted to a relatively small mining area at Merelani in northern Tanzania. The heat treatment applied to this example is standard and improves visual appeal, without diminishing its desirability among connoisseurs who understand that untreated material of equal color is exceptionally rare and commands a premium. The included clarity grade, when set as a cabochon, becomes a character feature that affirms natural origin and can provide interesting internal reflections and depth, while the excellent polish ensures that the surface presentation is refined and suitable for high quality jewelry projects. At The Natural Gemstone Company we document provenance and provide detailed specifications for each piece, and we are available to supply additional photographs, measurements or independent certification upon request, allowing buyers to make well informed decisions. This violet tanzanite is well suited to collectors seeking a museum quality specimen, to designers looking for a dramatic focal stone for a bespoke piece, and to investors who appreciate the finite geographic supply and strong market interest in well colored, sizable tanzanite specimens.