Ooops.  Cross-posted by Biscuits while I was composing.  Biscuits, I have a workable solution for P8/PP2010 which will cast sufficient light, yet not blow out to white.

    For P8 (and Poser Pro 2010), we'll need to conceal the IDL emitter inside the jewel, the jewel will need to be opaque, and set to not cast shadows.

     I'll work up a prototype when I get back home, and post a wireframe screenshot to show the spatial relationship of the jewel, emitter, and aura, along with material room screenshots to show the materials.

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5