Physical Properties
Chemical formula Al(OH)3
Class Hydroxide
Crystal system Monoclinic
Habit Coatings
Granular aggregates
Colloform masses
Radiating masses
Tabular, with pseudohexagonal shape
Color White or gray to greenish
Hardness 2.5 to 3.5
Specific gravity 2.40
Cleavage/fracture Perfect (001)
Luster Vitreous
Transparency Transparent to translucent
Streak White
δ 0.02
PPL Colorless
XPL Up to upper 1st order
after Perkins, 378

Gibbsite in Hand sample

Gibbsite in bauxite

Gibbsite in Thin Section

Gibbsite, plane polars

Gibbsite, crossed polars

Further Reading

Gibbsite at
Gibbsite at