group garnet system isometric formula Ca3Fe2(SiO4)3 optic uniaxial / biaxial Too-Vee 0 - 90¡ relief.1 high pos min. index 1.850 / 1.890 color colorless pleochroism no birefringence.1 anomalous cleavage no elongation no extinction *** angle *** alteration chlorite, hornblende, epodote, and iron oxides habit.1 euhedral occurence ignoeus (alkalic), hydrothermal, metamorphic (carbonate, skarn) TwoV 1 2 relief 3 pleochroism.2 birefringence cleavage.2