In the Article "Mineralogy,"in the Encyclopædia Britannica, written by Professor Heddle, of St. Andrew's, that gentleman gives the formula of Zoisite :—

4 CaO, 3 Al2O3, 6 SiO2+H2O.

Alumina 29·8; Lime 24·35; Oxide of Iron 2·8; Silica 40·3; and Water 2·1.) Cleavage, brachy-diagonal, perfect : H=6, G—3·2 to 3·4. White, brownish gray, and dark green. Localities, Glen Urquhart , Dalnein (Grantown), and Alt Gonalan, Inverness-shire ; Sterzing in Tyrol, the San-Alp in Carinthia, the Urals, and Connecticut.