"It’s only the combination of losing her newfound toy and Amethyst’s “realness” that unlocks her inborn ability, an ability that might be unique among Era 2 Peridots because our Peridot is the only one on a planet that allows Gems to break their mold. Say goodbye to self-pitying Peri and hello to Steven Universe’s first metalbender, a now-formidable force who’s only going to become more confident in herself and new rebel identity." -4Chan
I'm sure this will be looked into in future episodes.
"We all want progress, but if you're on the wrong road, progress means doing an about-turn and walking back to the right road; in that case, the man who turns back soonest is the most progressive." ~CS Lewis