The texture file for experience orbs has not been split up into individual files, unlike many other texture files containing multiple textures. It appears that this texture has been left out when most splittings occurred (the terrain.png and items.png splitting in 13w02a, and the splitting of the paintings file and particles.png in 1.14's development). This forbids the creation of animated orb textures, among other things.

Attached are split versions of the experience orb textures, excluding the five unused copies present in the texture sheet. I have not attached the texture sheet itself since this may possibly be considered unlawful asset redistribution (if this site is exempt from such restrictions please let me know - the split textures are a derivative work and as such should probably be acceptable) but the last five slots are clearly taking up unneccessary space which could be avoided with a splitting.