I
Pink held by manganese
The rubellite zone derives its rose tone from trace manganese (Mn³⁺) substituting in the octahedral sites—concentrated at the c-axis core.
II
Green bound by chromium
The verdelite rind owes its bottle-green lustre to chromium and iron absorption bands, thinning toward the prism faces yet never fully vanishing.
III
A boundary drawn in trace elements
The pink → green transition is neither sharp nor gradual—it follows the crystallographic growth zones that shift during a single cooling event.
IV
Polished on black velvet
Once cleaved and polished, the slice is mounted on the black gem-tray ground—the plate's dark substrate against which colour saturation is judged.