This bead is neat - like crackle glass, except the crackles are red? The clear part shifts to a ghostly blue under UV. 

This is part of the fauxfire collection - 80 uv-reactive or glow-in-the-dark shinies! All of the UV-reactive pieces will react under 365nm UV light; some will react differently or not at all under 395nm UV light. 

Want to add a set of UV flashlights to your order?