Fluorescent Blue Slag?

[Chordus]

I've run across a marble with a strange combination of traits.  The picture makes it look like a WV swirl, but in real life, it looks like a slag.  Not "it might be either," but almost irrefutably a slag when under normal light.  Problem is, it's got a brilliant yellow vein of glass when put under a black light, which is definitely not a quality of any blue slag I've run across.  It's part of the blue glass that's glowing, not the white strands.  I think I vaguely recall that Jackson made dark blue swirls which fluoresced...  is that what this might be?  Any other guesses?

[wvrons]

Not Jackson.  Jackson made a clear base with nice bright blue and nice white, which do not glow. Jackson made a dirty or crème white base with a more dull looking blue. This dirty crème white is a certain color and type of Vitrolite which does glow.  All the Jacksons which glow will contain this dirty creme looking white cullet from Vitrolite glass.  From the pictures your marble looks like Jabo. The  pattern especially the second picture looks Jabo.  Lots of Jabo classics had clear. Lots of Jabo classics and newer Jabos  glow. Jabo used lots of Fenton Art Glass cullet which glows. Not much of the marble above fits vintage slags. But very much of the marble above fits Jabo traits.  A blue and white vintage slag where the some of the blue glows would be very unusual. if it is irrefutably a slag ? Then you might call it a Jabo slag. 

[Chordus]

Jabo does make a certain amount of sense for the fold.  I'm 90% sure you're dead on, but everything but the glow and the fold is a dead ringer for a slag.  I guess that's a pretty huge "but" though!

The reason Jabo didn't register as a possibility is that the lot this comes from is almost exclusively MFC and Akro (mostly slags), WV swirls, plus a couple of CACs and Pelts for good measure (two CAC opaques!).  The set is quite incredibly overall...  the only outliers are this marble and the two I have in the other post.  The set's from eBay, so it's plausible that something else worked into the set (not an estate lot of known age).  I guess I'll throw this one in my "valueless but still pretty" set.

[slagmarble]

Not a slag...

Fluorescence is only really useful for slags on vaseline (green and yellow) and yellow (Christensen) or orange slags.  The former turns green, the latter will turn orange in areas particularly on yellow.

[sclsu]

Any thoughts on Ravenswood for this one?