Tough - Difficult to break apart as shown by fibrous minerals and most metals.
Habit:
Earthy - Dull, clay-like texture with no visible crystalline affinities, (e.g. howlite).
Habit:
Spherical - Spherical, rounded aggregates.
Habit:
Stalactitic - Shaped like pendant columns as stalactites or stalagmites (e.g. calcite).
Hardness:
2.5-3 - Finger Nail-Calcite
Luminescence:
Non-fluorescent.
Luster:
Vitreous - Pearly
Streak:
white
Optical Properties of Gibbsite
Gladstone-Dale:
CI meas= 0.033 (Excellent) - where the CI = (1-KPDmeas/KC) CI calc= 0.069 (Fair) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2356,KPDmeas= 0.2446,KC= 0.2531 Ncalc = 1.58 - 1.62
Optical Data:
Biaxial (+), a=1.568-1.57, b=1.568-1.57, g=1.586-1.587, bire=0.0170-0.0180, 2V(Calc)=0, 2V(Meas)=0-5. Dispersion r > v or r < v.
Pleochroism (x):
colorless.
Pleochroism (y):
colorless.
Calculated Properties of Gibbsite
Electron Density:
Bulk Density (Electron Density)=2.41 gm/cc note: Specific Gravity of Gibbsite =2.35 gm/cc.
Fermion Index:
Fermion Index = 0.0003011748 Boson Index = 0.9996988252
Photoelectric:
PEGibbsite = 1.10 barns/electron U=PEGibbsite x rElectron Density= 2.65 barns/cc.
Radioactivity:
GRapi = 0 (Gamma Ray American Petroleum Institute Units) Gibbsite is Not Radioactive
Gibbsite Classification
Dana Class:
06.03.01.01(06)Hydroxides and Oxides Containing Hydroxyl
Chemical Formula: 
