1.60 Carat Natural Cobalt Blue Spinel – Tanzania

A distinctive 1.60 carat natural cobalt spinel from Tanzania, displaying a sophisticated deep blue color with brighter blue flashes as the stone moves through the light.

Cut in an octagonal step-cut, the stone has a strong geometric appearance with broad, structured facets that emphasize its depth of color. Cobalt-bearing blue spinel occupies a particularly interesting niche within the spinel family, with fine natural examples sought by collectors for their unusual blue coloration and relative scarcity.

The accompanying gemological report identifies this specimen specifically as Natural Cobalt Spinel, with Tanzanian origin and no indication of heat treatment.

Gemstone Details

• Gemstone: Natural Cobalt Spinel
• Weight: 1.60 carats
• Color: Blue
• Origin: Tanzania
• Cut: Octagon Cut
• Measurements: 6.54 × 5.77 mm (see report for complete depth measurement)
• Treatment: No indication of heat
• Hardness: 8 on the Mohs scale
• Condition: Loose gemstone
• Report: AIG – American International GemLab
• Report No.: GEM20260827178198

A Collector’s Blue Spinel

Blue is among the more unusual colors found in natural spinel. In certain blue spinels, cobalt can contribute to the characteristic blue coloration that has made cobalt-bearing material particularly interesting to gemstone collectors.

Unlike blue sapphire, spinel is singly refractive, giving well-cut stones their own distinctive optical character. With a hardness of 8, spinel also combines rarity and beauty with enough durability to make it suitable for fine jewelry.

This specimen’s octagonal step cut creates a completely different appearance from the more common brilliant-style spinel, producing broad flashes of blue and emphasizing the stone’s architectural geometry.

Natural & Unheated

The report states “No Indication of Heat.” The stone is sold as the exact loose gemstone pictured, allowing the buyer to preserve it as a collector specimen or commission a one-of-a-kind ring or pendant around it.

Offered at $3,500

Macro photography is used to show the gemstone in detail. Magnification and lighting can reveal inclusions and internal characteristics that may be considerably less apparent during normal viewing.