I recently got ahold of the official iOS Human Interface Guidelines by Apple. But with a twist - they were from May 2013. They actually had 218 pages worth of guides discussing icongraphy and a lot of system elements from iOS 6 and why they're designed that way aswell as their functional purpose.
If you actually want to download and go through the Human Interface Guidelines then go ahead you can download them right here.
While it may be fun to go through these 200+ pages for no reason, I'm actually posting this so people can use this as help to learn proper graphic design and app design (Or system element design for that matter) that actually resembles iOS 6. I wish I found this earlier but I did only a year ago. This has greatly helped me to better work on my accuracy regarding my applications, concepts and icons.