Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).
Hardness:
1.5-2 - Talc-Gypsum
Luminescence:
Non-fluorescent.
Luster:
Earthy (Dull)
Magnetism:
Nonmagnetic
Streak:
light yellow
Optical Properties of Humboldtine
Gladstone-Dale:
CI meas= -0.784 (Poor) - where the CI = (1-KPDmeas/KC) CI calc= -0.761 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2521,KPDmeas= 0.2554,KC= 0.1432 Ncalc = 1.33