Board Thread:Speculation House/@comment-29781768-20180104044655/@comment-30573883-20180119174137

IT stated that Her Semblance, according to Rooster Teeth, is telekinetic manipulation of sand and dust (normal dust, not the crystalline Dust), and that her most common application of this is using it to shape hot sand into glass, in conjunction with her Fall Maiden fire-manipulation abilities. She apparently uses heat to melt the sand togather (either from her Maiden abilities or the Dust she enhances her clothing with), and uses her Semblance to reshape it into glass, which in the process hardens the glass into makeshift obsidian that, when strengthened ny her Aura, can resist metallic.

Check RWBY Characters salem's faction on tv tropes and it will be on cinder's part that says Dishing Out Dirt if you do not believe me.