It could also be a wooden finial.
Of the staffs I have seen, several had wooden, field made finials, (some staffs were mere limbs, a few still with bark). A fellow researcher also sent me his notes of the staffs at Tredegar and MOC, which shows the same.

On a side note, I had kin in the 39th Mississippi at Allatoona. Have seen no mention yet of the regimental colors in the several letters I have from members of the regiment.