Board Thread:Off Topic/@comment-24993958-20151118083252/@comment-23702983-20151120041536

She was clearly using dust to produce those crystals. You see her pull a vial of dust out and scatter it around her, which turns into the crystals and fires. It's clearly not obsidian.

It still doesn't explain how she was able to manipulate fire to that degree, or remotely, without using dust. She called fire up from underneath their feet without being near it. She materialized weapons from fire and solidified them. It's possible that obsidian has something to do with her semblance, since obsidian is found in volcanic ash, or possibly carbon based. Her shoes also have a black glass crack-like pattern to them, and when she vanishes after her fight with Ruby, she leaves her mask on the floor and it makes a breaking sound when the guard walks by, almost like the sound of cracking glass or crystal. Might be obsidian based. So my guesses are, something to do with fire, volcanic, ash, obsidian, or carbon.