2.63 Carats Natural Cobalt Blue Spinel - Tanzania (Blue-to-Purple Color Change)

An extraordinary 2.63-carat natural cobalt spinel from Tanzania, distinguished by a documented blue-to-purple color change. Under different lighting conditions, the gemstone transitions from a deep cobalt-blue appearance toward rich violet and purple tones, giving the stone two distinctly different personalities.

The gemstone has been fashioned into a heart faceted cut, an uncommon and visually striking presentation for a cobalt spinel of this size. Its faceting produces flashes ranging from midnight and royal blue to brighter electric-blue highlights, while the alternate lighting appearance introduces violet and purple.

The accompanying gemological report identifies the stone as NATURAL COBALT SPINEL (COLOR CHANGE) and records “No Indication Of Heat.” The report further notes that the color change can be observed under incandescent lighting.

Cobalt-bearing blue spinel occupies a distinctive position among collector gemstones. Unlike ordinary dark-blue spinel, desirable cobalt spinel derives its celebrated blue coloration from the presence of cobalt within the crystal structure. Stones combining substantial size, documented cobalt identification and a noticeable color-change phenomenon represent an especially interesting category for serious colored-gem collectors.

Natural internal characteristics remain visible and have not been concealed in the photography.

Gemstone: Natural Cobalt Spinel (Color Change)
Weight: 2.63 carats
Origin: Tanzania
Color: Blue to Purple
Shape/Cut: Heart Faceted Cut
Measurements: 8.30 × 9.01 × 5.44 mm
Hardness: 8.0
Treatment: No Indication of Heat
Color Change: Observed under incandescent lighting
Condition: Loose Gemstone
Price: $6,000

At 2.63 carats, this is a substantial cobalt spinel combining an unusual heart cut with Tanzanian origin and documented blue-to-purple color change. It can stand alone as a collector specimen or become the centerpiece of a one-of-a-kind fine-jewelry design.