Sillimanite
Sillimanite is a naturally occurring alumino-silicate mineral, with the chemical formula Al₂SiO₅.
➡️ It is one of three polymorphs of aluminium silicate — the other two being Kyanite and Andalusite.
Polymorphs = same chemical composition but different crystalline structures, formed under different pressure-temperature conditions.
Geological Formation of Sillimanite
Where does it come from?
- Sillimanite forms under high-pressure and high-temperature conditions.
- It is typically associated with the metamorphism of clay-rich or aluminous rocks.
- Commonly found in rocks such as:
- Schist
- Gneiss
- Granulite
Industrial Applications of Sillimanite
Now, why is this mineral important?
Sillimanite has outstanding thermal stability, which makes it ideal for industries dealing with extreme heat.
Here’s where it is used:
| Industry | Use |
|---|---|
| Ceramic Industry | For high-quality ceramics that endure thermal shocks. |
| Glass Industry | As a heat-resistant additive in glass melting tanks. |
| Metal Industry | In furnace lining, kilns, refractory bricks, and other high-temp environments. |
| Electrical Industry | Low electrical conductivity makes it useful in insulation. |
| Gemstone Use | Rarely used as a gemstone (for collectors), but not widely available commercially. |
➡️ From steel plants to space tech, if high heat is involved — sillimanite is the saviour.
Reserves and Production in India
India is richly endowed with sillimanite, and is a leading global producer.
✅ Reserves (2020):
72.26 million tonnes
| State | Share of Resources |
| Odisha | 24.49% |
| Tamil Nadu | 24.01% |
| Uttar Pradesh | 15.84% |
| Andhra Pradesh | 15.31% |
| Kerala | 9.57% |
| Assam | 6.37% |
🔍 Focus Area: Odisha and Tamil Nadu together hold nearly half the total reserves.
Production Status (2020–21)
| Metric | Value |
| Total Production | 1,437 tonnes |
| Top Producer | Maharashtra |
Trade: Exports and Imports
| Type | Major Countries |
| Exports | China (73%), Japan (18%), Nepal (5%), |
| Imports | Somalia (86%), USA & Poland (7%) |
➡️ Despite being a leading producer, India still imports small amounts — possibly of refined or specific-grade sillimanite for niche industries.