|Source Play Store|
Let we see the Groups app.
It has a circle app icon and it look more in the iPhone iOS look. You can recognize the idea of the mind bubble. Light gradients and powerful colors. Facebook Groups use the same icon for iPhone and for Android, wich is not correct if you check the new Material Design guidelines.
|Image copyright Sociotrope.com|
Here is a example how it have to be for Android. The idea comes from the Material Design: "Product icon design is inspired by the tactile and physical quality of material. Each icon is cut, folded, and lit as paper would be, but represented by simple graphic elements. ... The matte-like finish interacts with light through subtle highlights and consistent shadows." Maybe Facebook Creative Lab will change the icon in future for Android phones.