calcite mineral class
-isomorphism can exist with minerals which are not in the same mineral class--since they are not in the same mineral class they cannot be in the same isomorphic group--NaNO 3 (nitratite) is isomorphic or isostructural with the minerals in the calcite group of the carbonate class including siderite and calcite 2. polymorphic group is a mineral group belonging to the same mineral class, all having the