[IC] Chapter 2-5: You're whirling 'round...

[DM Surranó]

Bright it is, indeed, but the spherical form somehow seems to be part of the wall, not encased into it. It is quite clear for any dwarf worth their ore that the "gem" is actually part of the picture, made of the same stone, it's just the intricate colors that make it look like a finely cut gem. The coloring actually makes the sensation as if light would pass through the gem and refract around the nearby parts of the relief and being scattered as if it would be green light... but the picture is not emitting light, nor does it reflect light, it's just really, really intricate artwork. (and as such, probably heart-warming for the dwarves)