User blog comment:VedranTheII/Pretentious Diaries 2: What tricks would you teach your Aura?/@comment-26512661-20150718155058/@comment-25555436-20150718183802

"Carbon" would make some sense, if it's something like Earth Dust+Fire Dust. Although IIRC, burning carbon would give you Cal instead, which is more white.

However, Obsidian also makes sense in the same way, Earth Dust+Fire Dust.

However, got to agree with Jay here anyway. Obsidian does work for weapons, the Aztecs even used it for their weapons. Carbon....not so much.