Hackmanite (tenebrescent sodalite) 7.7g fluorescent

A hackmanite rough with a notably cool blue-lavender color in white light, covering the full body with very little visible matrix. The tone reads as periwinkle or blue-violet rather than the warmer pink-mauve typical of this material, giving it a distinctly different character among the specimens in this series. After UV exposure the color shifts to a warmer purple-violet, losing the cool blue quality and deepening toward a more conventional hackmanite purple. Under longwave UV (365nm) the piece fluoresces brilliant orange-yellow across the full surface.

Tenebrescence is the reversible color change that distinguishes hackmanite from ordinary sodalite: white or pale grey in darkness, shifting to pink or violet under UV or sunlight, bleaching back in ordinary light. The cool blue-lavender white-light tone of this specimen is an expression of the hackmanite's individual crystal chemistry rather than a different mineral; the tenebrescent shift and the strong orange fluorescence at 365nm confirm the identification. The shift from a cool blue-lavender in white light to a warm purple after UV is itself an additional visual dimension not seen in the warmer-toned specimens. From Badakhshan, Afghanistan.

• Stone type: Natural hackmanite (tenebrescent sodalite)
• Weight: 7.7g
• Size: 30x16x17mm
• Color: Blue-lavender (white light); purple (after UV)
• Fluorescence (365nm): Strong orange
• Cut: Rough
• Clarity: Opaque
• Treatment: Untreated
• Origin: Afghanistan

Natural hackmanite, tenebrescent sodalite, Afghanistan, sold loose.