User blog comment:Demetri Anacona/Aura- What to consider for anyone putting aura in their OC or anything for that matter/@comment-24087318-20140112181206

It's not known in Canon if one can unlock their aura solely through training and practice. As far as we know, everybody has to have it unlocked by another person.

In addition, while there is no canonical, proven relationship between Semblances and Aura, there is evidence they are connected. When you see Ren fighting the King Taijitu and exerting quite a bit of Aura during the fight, he's worn down. And for the rest of the Initiation, he's notably more tired than anybody else, out of breath when he and Nora get to the artifacts, and by the end he outright collapses.

In this same arc, we see Weiss during the Nevermore finale using quite a bit of her Semblance, running not one, but an entire string of Glyphs up the side of the cliff face. In the frames she's seen after this, she's fatigued, doubled over and out of breath.

Due to both of these exertions having the same physical symptoms, it is likely evidence that Semblance and Aura usage are tied to eachother, possibly that using ones Semblance uses Aura as energy.

You forgot to mention, during the Weapon Conduit part, that it's likely that in order for a weapon to DO this, it needs to remain in physical contact with its user. Blake and Penny use a ribbon, and a series of strings respectively to stay in contact with their weapon. And while Pyrrha has thrown her spear, she has her Semblance to easily retrieve it, and in combat, has only thrown it at the eyes of a Deathstalker, a critically weak and fleshy point.

It's also likely that, due to the aformentioned contact thing, bullets and thrown weapons are not effected by it. Which is likely why the Blade, and other melee weapons, did not phase out of use when Guns were invented.

Also...as Calamity Y said, it's Pyrrha, not Pyrrah.