Encrustations - Forms crust-like aggregates on matrix.
Habit:
Platy - Sheet forms (e.g. micas).
Hardness:
2 - Gypsum
Luster:
Pearly
Streak:
white
Optical Properties of Angastonite
Gladstone-Dale:
CI meas= 0.043 (Good) - where the CI = (1-KPDmeas/KC) CI calc= -0.014 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2464,KPDmeas= 0.2324,KC= 0.2429 Ncalc = 1.57 - 1.6