How in the heavens did Peridot crack her gem? She should have proceeded with caution, I guess. (And I apologize if you've already answered this question previously).

That actually came from an ongoing RP with my fiance and his awesome Ronaldo! After a stretch of time enjoying the individuality human culture encourages (and reinforced by ego-boosting from her “partner”), Peridot made the daring decision to destroy her OWN things: to return to the Kindergarten and render it beyond the simple repairs she would have had to make on it herself, to buy the humans time if/when the Homeworld sent reinforcements.

But that red goo that spilled back in On The Run had a side-effect, which they found underground in a facet untouched by the Crystal Gems:

This asshole

The confrontation ended up a lot worse than expected, and Peridot made sure her human companion was out of harm’s way, hooray for floating appendages!

Did I say hooray? I meant DEEP HURTING

He found Peridot’s cracked gem and on the desperate theory it could be saved, he let the secret out to Steven. The best part was after she regenerated:

Steven you filthy shipper trash omg

Bonus: Until Peridot shapeshifted back into the more familiar and comfortable work form, hands for shoosh papping Ronaldo weren’t the only thing she popped back with in her default form:

she is very smoll