Talk:Cinder Fall/@comment-130.105.235.70-20160609112443/@comment-4010415-20160609125746

The glass was pretty much Cinder melting sand and dirt with her Dust. The black glass is obsidian, so it's possible that she could've used Dust to make lava and then controlled it with her Aura to super-cool it into obsidian in whatever shape she wanted.

Like Spirited said, the writers were trying to convey to us that glass is not her Semblance.