group phyllosilicate
system orthorhombic
formula Ca2Al(AlSi3O10)(OH)2
optic biaxial pos
Too-Vee 64 - 70¡
relief.1 high pos
min. index 1.610 / 1.670
color colorless
pleochroism no
birefringence.1 0.020 - 0.035
cleavage yes
elongation no
extinction parallel
angle 0¡
alteration chlorite, zeolite
habit.1 tabular, fibrous, acicular
occurence igneous (volcanic), metamorphic (low grade, contact, carbonate)
TwoV 2
relief 3
pleochroism.2
birefringence 5 8 9 10 11 12 13
cleavage.2 {001} good, {110} poor