The minerals in question are the Phakolite of the Bohemian Mittelgebirge, and Caporcianite, a newly discovered mineral, first observed by Dr Savi, in a copper-mine at Caporciani, in the valley of Cæcino. The author found, that in point of composition, Caporcianite belongs to that division of the zeolites, which comprehend Analcine, Ledererite, Potash-harmotome, Chabasie, and Levyn, and whose constitution is represented by the mineralogical formula r S2+3 AS2 + z A q,—z being a variable quantity, r representing the variable monatomic bases, and A & S alumina and silica.