User blog comment:SomeoneYouUsedToKnow/SYUTK's V5E12 - OOOOOOOOOOOOOOOZZZZZZZZZZZZZZZZZPPPPPPPPPPPPPPPIIIIIIIIIIIIIIIIIINNNNNNNNNNNNNNNNNN - Impressions/Recap/@comment-27144409-20180111003140/@comment-26397825-20180111023639

Actually, it was another fan that said that apparently RT said what Cinder's semblance is. The fan also said he was trying to remember something from over a month ago (at the time), and it was at a panel in Germany that pretty much no video footage has emerged from. So we can't confirm or deny that such a thing was said at the panel, so it's currently being treated as 'this would be cool, but we dunno if it's true.'

Now, as for what they said it was...they said it was controlling normal dust. That's it. We don't know what level of control, or if she can reshape it (though I believe that the reshaping is because of the fire dust she uses in conjunction with it to make it glass, and it's basically just telekinetic control of dust and dust particles.