Figure 3. The infrared absorption spectra of a rare 0.2 ct
rough “prismatic” synthetic amethyst from Russia
(Am004; see figure 2, left) are shown at resolutions of 4
cm–1 (red) and 0.5 cm–1 (black). The 3595 cm–1 band is
not observed, but a shoulder is present at 3543 cm–1.