Board Thread:Off Topic/@comment-24993958-20151118083252/@comment-25396609-20151120042049

Dust can be used to spontaneously create ice and solid stone, obsidian is well within that capacity, which is why Chish is so insistent about lava dust (which if real could be used to create obsidian)

As for the rooftop, her dress did glow and we kow for a fact it uses dust, she may have used dust from the dress when blocking the prohectiles from Glynda, and used the residual energy for the under foot blasts.