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out of the melt, 2
 

image

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Fig. 8. Same as Figure 7 with Crossed Nicols
illustrating H. C. Arnold, Investigation of Willemite-Tephroite Soda Glass. Transactions of the American Ceramic Society, Vol XIX. (1917): 674-695

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.
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15 February 2013 *
tags: Arnold, H. C.; extinction, parallel; rounds; transactions; willemite; Zn2SiO4