Rossmanite occurs as pink crystals in the pegmatite. It forms in the late stages of crystallization.
The compositions of individual analyses in the rossmanite field are indicated by the following diagram:
Selway JB, Novák M, Cerný P, Hawthorne FC. (2000) Compositional evolution of tourmaline in lepidolite-subtype pegmatites. European Journal of Mineralogy, 11, 569-584.