AstraZeneca today announced that the US Food and Drug Administration (FDA) has issued a Complete Response Letter (CRL) regarding the New Drug Application (NDA) for sodium zirconium cyclosilicate
(ZS-9), the investigational medicine being developed for the treatment of hyperkalaemia (high potassium level in the blood serum) by ZS Pharma, a wholly-owned subsidiary of AstraZeneca.
When we get to "The Nesosilicate Subclass" we find, within it, about 20 pages on Imperial topaz and the history of its extraction at Ouro Preto; when we come to "The Cyclosilicate
Subclass" we find 12 pages (3 short chapters) on emeralds, 30 pages (two chapters) on other colored beryls, and an extraordinary 100 pages on tourmalines, including individual chapters on, for example, the Cruzeiro mine, the Pederneira mine, the Santa Rosa mine, the Jonas mine, the Golconda district, northeastern Brazilian tourmaline-bearing pegmatites, and miscellaneous occurrences of uvite, dravite and schorl.
In his commentary on the poem, Italo Calvino points out that emerald is a kind of beryl (a cyclosilicate
containing beryllium) and concludes that the whole line is based on approximate homophony, identifying the lude as: "Au beryl d'emeraude un glucinium" (Calvino 163-164).