So, I liked either the reversed dual color, #[2] (4th), or #[1] 3D version.
I am inclined to keep purple as the main color but could be convinced otherwise.
Also, no need to resemble the gem. We could do a low poly ostrich with hard corners in purple to represent the gem. Kinda like this: 
Not sure which my logo versions your're refering to as the "4th". Is it the bottom right version on dark background?
(can you point that out on my image please).
I like purple will work on a purple version.
With regard to the ostrich I think it might be hard to achive a simplify version that could be used as a logo/icon, I'm trying to visualize how it would work in small sizes like the 96x96px app icon
Purple - I like it better than my initial blue color scheme
