Al(OH)3

• Monoclinic 2/m
  
  • Uniaxial (+)
    
• Form and Cleavage: Crystals have twinning in four planes and one plane of cleavage.
  
• Color Properties: White, gray, light pink, green, or brown.
  • White streak and vitreous to earthy luster.
    
• Optical Properties: Biaxial (+) and colorless
  
• Occurrence: Produced in tropical soils through the weathering of feldspars and other aluminum bearing minerals.