out of the melt, 2
Figure 8 is a picture of the same crystal under crossed nicols. They show parallel extinction, and high birefringence. Judging from the shape of the end of these crystals one would say that the liquid had high surface tension.
Artificial willemite was used as the basis of first generation fluorescent tube phosphors.
fluorescence; extinction, parallel; rounds; willemite; Zn2SiO4; H. C. Arnold