Diaspore (α-AlO(OH)) is a naturally occurring aluminium oxyhydroxide mineral and a major constituent of certain bauxite deposits. It represents the most structurally stable and hardest of the three primary aluminium-bearing minerals found in bauxite, alongside gibbsite and boehmite.
Due to its dense crystal structure and strong hydroxyl bonding, diaspore requires significantly higher temperature and caustic conditions for alumina extraction, making it the most challenging bauxite mineral to process in aluminium refining.
Composition & Mineralogy
| Parameter | Description |
|---|---|
| Chemical Formula | α-AlO(OH) |
| Mineral Type | Aluminium oxyhydroxide |
| Crystal System | Orthorhombic |
| Alumina Potential | High (~85% Al₂O₃ equivalent when calcined) |
| Associated Minerals | Hematite, goethite, silica, gibbsite, boehmite, rutile |
Physical Properties
| Property | Typical Range |
|---|---|
| Color | White, grey, yellowish, greenish, brown, pinkish |
| Crystal Habit | Platy, elongated, tabular, acicular |
| Hardness (Mohs) | ~6.5 – 7 |
| Specific Gravity | ~3.1 – 3.5 g/cm³ |
| Cleavage | Perfect on {010}, distinct on {110} |
| Fracture | Conchoidal to uneven |
| Luster | Vitreous to pearly |
Mechanical Properties
Diaspore’s hardness and density significantly influence beneficiation and refining behavior.
✔ High hardness increases crushing and grinding energy
✔ Brittle fracture produces fine particles during comminution
✔ Perfect cleavage causes preferential breakage
✔ Decrepitation may occur during heating due to structural water loss
Strengthening & Metallurgical Behavior
Diaspore does not act as a strengthening additive; however, its metallurgical behavior is critical in aluminium extraction and refractory production.
Metallurgical Characteristics:
✔ Requires high-temperature, high-pressure Bayer digestion
✔ Dissolves more slowly than gibbsite and boehmite
✔ Often requires beneficiation to improve Al/Si ratio
✔ Dehydrates upon calcination to form corundum (α-Al₂O₃)
Refining & Processing Properties
Industrial Processing Challenges:
✔ Higher caustic soda consumption
✔ Increased energy demand
✔ Lower digestion kinetics without beneficiation
✔ Common use of flotation to remove silica impurities
Diaspore-rich bauxites are typically processed in refineries designed for high-pressure digestion and optimized heat recovery.
Key Characteristics
✔ Highest hardness among bauxite minerals
✔ Excellent thermal stability
✔ High alumina yield potential
✔ Suitable for refractory-grade alumina
✔ Strong resistance to chemical attack
Available Forms
Natural:
Diaspore-rich bauxite ore
Natural diaspore crystals (rare gem quality)
Processed:
Beneficiated bauxite concentrates
Calcined diaspore alumina (refractories & ceramics)
High-purity α-Al₂O₃
Applications
Industrial Uses:
✔ Aluminium production (as part of bauxite feedstock)
✔ Refractories and kiln linings
✔ Advanced ceramics and high-temperature materials
✔ Abrasives (limited use)
✔ Catalyst and specialty alumina precursors
Specialty Uses:
✔ Gem-quality diaspore (Zultanite / Csarite) for jewelry
Advantages of Diaspore Bauxite
✔ High alumina potential after calcination
✔ Exceptional thermal resistance
✔ Mechanical durability
✔ Enables production of premium refractory alumina
✔ Unique optical properties in rare gemstone forms
Why Choose Diaspore Bauxite?
Diaspore bauxite is indispensable where gibbsite is scarce and high-temperature performance is required. While more demanding to refine, it delivers high-quality alumina suitable for aluminium production, refractories, and advanced ceramic applications.
Diaspore bauxite represents the most thermally and mechanically robust form of aluminium ore, playing a vital role in both metallurgical aluminium production and high-performance industrial materials.