Gibbsite
Mineral Al(OH)3
Also called Hydrargillite
About it
White to pale green crusts, stalactites, and pearly plates; a main part of bauxite, the ore of aluminium. Named for American collector George Gibbs; first found at Richmond, Massachusetts.
- Type
- Mineral
- Group
- Hydroxide
- Formula
- Al(OH)3
- Hardness (Mohs)
- 2.5–3.5
- Specific gravity
- 2.38–2.42
- Streak
- white
- Lustre
- vitreous (glassy), pearly
- Crystal system
- Monoclinic
- Colours
- white, grey, pale green, pale pink, pale blue
- Transparency
- transparent, translucent
- Cleavage and fracture
- perfect basal; tough
Typical values: real specimens vary. For more, see mindat.org.