(Science: chemical) a mineral, commonly of a yellowish green (pistachio) colour, occurring granular, massive, columnar, and in monoclinic crystals. It is a silicate of alumina, lime, and oxide of iron, or manganese.
The epidote group includes ordinary epidote, zoisite or lime epidote, piedmontite or manganese epidote, allanite or serium epidote.
Origin: gr. To give besides; over – to give: cf. F. Epidote. So named from the enlargement of the base of the primary, in some of the secondary forms.