You are right. I am sorry. I could not find any site in English about chalcedony stone and Hildegard of Bingen, so I posted that article. This is the original site in italian about chalcedony stone: [https://www.santa-ildegarda-di-bingen.it/it/pietre/pietre-preziose/article-calcedonio/](https://www.santa-ildegarda-di-bingen.it/it/pietre/pietre-preziose/article-calcedonio/)