Liddicoatite, ideally Ca(AlLi2)Al-6(SiO6)(BO3)(3)(OH)(3)F, is an extremely rare species of tourmaline, found in very few localities worldwide. A large (similar to 2 cm in cross section), euhedral sample of tourmaline retrieved from atop the Black Rapids glacier, Alaska, is shown to vary from a light pink elbaite in the core region, average composition (Na0.4Ca0.3 square(0.3))(Al1.75Li1.25) Al-6(BO3)(3)(Si6O18)F-0.4(OH)(3.6), to a pale green liddicoatite at the edge of the crystal, (Na0.3Ca0.6 square(0.1))(Al1.0Li1.6Fe0.2Mn0.2)Al-6(BO3)(3) (Si6O18)F-1.0(OH)(3.0). Detailed electron-microprobe analysis and B-11 and Al-27 Magic-Angle-Spinning Nuclear Magnetic Resonance spectroscopy show that several substitutions were active during growth, with (X)square + Al-Y -> Ca-X + Li-Y (liddicoatite-rossmanite solid-solution) and 2(Y)Al + (X)square -> 2(Y)M* + Ca-X accounting for most of the compositional variation. Throughout the tourmaline, there are instances of reversals in the trends of all major constituents, although few compositional gaps are observed. Most notably, a sharp decline in Ca content from similar to 0.35 to similar to 0.05 apfu (atoms per formula unit) with increasing distance from the core at similar to 2 mm from the crystal edge is followed by a sharp rise in Ca content (to 0.55 apfu), along with (Fe + Mn) content (from 0.01 to 0.35 apfu). In the core region, the origin of the Ca in the tourmaline is not clear; the correlation of Ca and F is consistent with both (1) a melt in which Ca was held as complexes with F, or (2) earlier contamination of the melt by a (Ca, F)-rich fluid. Close to the rim, a dramatic increase in Ca, F, Mn and Fe is probably due to late-stage contamination by fluids that have removed these components from adjacent wallrocks.