Board Thread:Speculation House/@comment-74.97.16.55-20170806201653/@comment-4010415-20170806215308

Ruby saying "I don't think it was her Semblance" was the writers' way of telling us her Semblance is not glass.

She makes the glass by using Dust to manifest lava and cool it into obsidian or by melting dirt/sand into glass.

The lava is Dust, not Semblance. There are literally bright orange Dust crystals in the volcanic biome in the colosseum, and her clothes lit up bright orange.