Irregular - Flat surfaces (not cleavage) fractured in an irregular pattern.
Habit:
Columnar - Forms columns
Habit:
Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite)
Habit:
Twinning Common - Crystals are usually twinned.
Hardness:
3-3.5 - Calcite-Copper Penny
Luminescence:
Non-fluorescent.
Luster:
Vitreous (Glassy)
Magnetism:
Nonmagnetic
Streak:
pale green
Optical Properties of Geminite
Gladstone-Dale:
CI meas= -0.021 (Excellent) - where the CI = (1-KPDmeas/KC) CI calc= -0.081 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2017,KPDmeas= 0.1906,KC= 0.1866 Ncalc = 1.65 - 1.69
Optical Data:
Biaxial (+), a=1.656, b=1.692, g=1.77, bire=0.1140, 2V(Calc)=72, 2V(Meas)=75. Dispersion weak, r > v.
Pleochroism (x):
colorless.
Pleochroism (y):
colorless.
Pleochroism (z):
green pale grayish.
Calculated Properties of Geminite
Electron Density:
Bulk Density (Electron Density)=3.51 gm/cc note: Specific Gravity of Geminite =3.71 gm/cc.
Fermion Index:
Fermion Index = 0.0001754138 Boson Index = 0.9998245862
Photoelectric:
PEGeminite = 35.88 barns/electron U=PEGeminite x rElectron Density= 126.04 barns/cc.
Radioactivity:
GRapi = 0 (Gamma Ray American Petroleum Institute Units) Geminite is Not Radioactive
Chemical Formula: 
