1. ppl albite twinning; zoned x5
1. ppl albite twinning; zoned x5
2. xpl albite twinning; zoned x5
3. xpl albite twinning; zoned x5
4. xpl pericline & albite twins x5
5. ppl plutonic plagioclase x5
6. xpl plutonic plagioclase x5
7. ppl plutonic plagioclase x5
8. xpl plutonic plagioclase x5
9. ppl microlites & devitrific. x10
xpl 20*
ppl 5*
group feldspar
system tetragonal
formula NaAlSi3O8-CaAl2Si2O8
optic biaxial neg / pos
Too-Vee 45 - 102¡
relief.1 low neg / pos
min. index 1.527 / 1.590
color colorless
pleochroism no
birefringence.1 0.007 - 0.013
cleavage yes
elongation no
extinction inclined
angle ***
alteration sericite, saussurite, scapo- lite, prehnite, calcite
habit.1 tabular (euhedral, anhedral)
occurence igneous, metamorphic, sedimentary
TwoV 1 2
relief 1 4
pleochroism.2
birefringence 1 3 4 5 6 7
cleavage.2 {001} perfect, {010} good, intersect 94¡