group pyroxene
system monoclinic
formula NaAlSi2O6
optic biaxial pos / neg
Too-Vee 60 - 96¡
relief.1 mod to high pos
min. index 1.640 / 1.692
color colorless
pleochroism yes
birefringence.1 0.006 - 0.021
cleavage yes
elongation yes
extinction parallel, inclined, symmetric
angle 32 - 55¡
alteration amphibole, analcime, nepheline
habit.1 columnar, fibrous, prismatic, tabular
occurence metamorphic (medium grade, regional)
TwoV 2 3
relief 2 3
pleochroism.2 green, yellow
birefringence 1 2 3 4 5 6 7 8
cleavage.2 {110} pyroxene cleavage at 87¡