Fig. 1. Crystals with needle-like dumortierite (a-c) and dyed crystal (d)

Fig. 2. Different crystal morphology and distributions of dumortierites in crystals. (a) At the bottom of crystal; (b) irregular shape; (c) radial shape; (d) irregular shape

Fig. 3. Counterfeit dumortierite inclusion in dyed crystal (a-c) and dumortierite in crystal (d). (a) Zooming 32 times; (b) zooming 64 times; (c) zooming 128 times

Fig. 4. Thin slices of crystal samples with dumortierite

Fig. 5. Distribution fitting diagrams of different elements in crystal slices

Fig. 6. Infrared spectra of crystal and dumortierite

Fig. 7. Raman spectra of crystal and dumortierite