User blog comment:VedranTheII/Pretentious Diaries 2: What tricks would you teach your Aura?/@comment-10380701-20150718080559/@comment-10380701-20150718113752

I assume because it's not part of the basic four, Earth Dust is something that isn't normally used, since in may be common standards for Dust sorcerers to rely on Ice Dust.

But yeah, Earth Dust is a pretty damn awesome defensive (and offensive is used right) Dust if utilized properly.