What is Boehmite?
Boehmite is one of the main aluminium hydroxide minerals in bauxite and lateritic weathering systems. It is usually fine grained, but botryoidal or foliated specimens can be attractive.
Mineralogy and structure
Boehmite has the formula AlO(OH) and an orthorhombic structure. Hardness is about 3-3.5 and specific gravity is close to 3.0. It is closely related to diaspore and gibbsite.
Colour and appearance
Colours range from white and colourless to yellow, brown and reddish shades caused by iron-rich impurities. Lustre is commonly pearly or dull, and crystal aggregates may be botryoidal or foliated.
Formation and localities
Boehmite forms in tropical weathering profiles, bauxite deposits, clay-rich sediments and some hydrothermal systems. Important deposits occur in Australia, Guinea, Brazil, Greece, Hungary, China and India.
Collecting and care
Fine-grained aluminium hydroxides are difficult to distinguish visually. Record the geological setting and use an analytical source when the exact phase matters; keep soft material protected from abrasion.
Boehmite and zodiac signs
Some modern crystal pages associate Boehmite with Virgo or Capricorn because of its pale colour and orderly layered structure. These are symbolic associations only.
Symbolic and esoteric associations
Boehmite may be used metaphorically to represent patience, weathering and gradual refinement. Such symbolism is cultural and not a property of the mineral.
