group tectosilicate
system tetragonal
formula see field properties
optic uniaxial neg
Too-Vee 0¡
relief.1 low to mod pos
min. index 1.532 / 1.571
color colorless
pleochroism no
birefringence.1 0.004 - 0.038
cleavage yes
elongation yes
extinction parallel
angle 0¡
alteration sericite, calcite, chlorite, epidote, zeolites
habit.1 prismatic, acicular, columnar, granular
occurence metamorphic (contact, regional, skarn)
TwoV
relief 1 2
pleochroism.2
birefringence 1 2 3 4 58 6 7 8 9 10 11 12 13
cleavage.2 {100} good, {110} fair, intersect at 45¡