Key points are not available for this paper at this time.
Epidote-group minerals are monoclinic in symmetry and have topology consistent with space group P2 1 /m and the general formula A 2 M 3 T 2 O 7 TO 4 (O,F)(OH,O). Zoisite is an orthorhombic polymorph of clinozoisite Ca 2 Al 3 Si 2 O 7 SiO 4 O(OH) and is thus not considered a member of the epidote-group. Epidote-group minerals are divided into three subgroups. (1) Members of the clinozoisite subgroup are derived from the mineral clinozoisite Ca 2 Al 3 Si 2 O 7 SiO 4 O(OH) by homovalent substitutions only. The key cation-and anion-sites are A1
Armbruster et al. (Mon,) studied this question.