This gem is unlocked in the level "Draggin' On" within "Tranquility Falls". In order to unlock this gem, you have to complete the entire level without destroying any boxes (including checkpoint boxes). You can die as many times as needed however (and can use the bonus route as a checkpoint by going into it and then dying).
Once you reach the end of the level, the blue gem will appear in front of the crate that says how many boxes you have broken.
Note: The achievement will unlock after completing the level.
Note: Do not attempt on inverted mode as it will not work.
In case any of you like a video guide as well, please see below a video guide, courtesy of Maka91: