Gibbsite

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 grey to greenish
Hardness 2.5 to 3.5
Specific gravity 2.40
Cleavage/fracture Perfect (001)
Uneven
Luster Vitreous
Pearly
Earthy
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

Stay tuned!

Further Reading

Gibbsite at mindat.org

Gibbsite at webmineral.com