Physikalische Eigenschaften
Habit: prismatic according to b, striated, columnar.
Color: gray, apple green, brown, blue,
or rose red.
Diaphaneity: transparent to translucent.
Luster: vitreous (i.e., glassy),
resinous, pearly.
Streak: white.
Cleavage: [001] perfect, [100] imperfect.
Fracture: uneven.
Chemical: insoluble in strong mineral acids, but attacked by HCl after calcination giving
a gel of silica, fusible giving a dark green globule.
Occurrence: regional metamorphic and
pegmatite rocks.
