Agalite is an old synonym for talc, specifically a fine fibrous variety sometimes pseudomorphous after enstatite. In mineralogical literature, the name has largely fallen out of use, but you may still encounter it in historical texts or industrial contexts.
🌍 Origins and Naming
- First Known Use: Around 1878
- Name Origin: The etymology is uncertain, but “agalite” was applied to fibrous talc varieties.
- Synonym: Today, it is recognized simply as talc (Mg₃Si₄O₁₀(OH)₂).
🔬 Chemical and Structural Properties (Talc / Agalite)
- Formula: Mg₃Si₄O₁₀(OH)₂
- Crystal System: Monoclinic or triclinic (depending on polytypes)
- Color: White, gray, greenish, or brownish
- Habit: Massive, foliated, fibrous (agalite refers to fibrous talc)
- Hardness: 1 on Mohs scale (softest mineral)
- Specific Gravity: ~2.7–2.8
- Luster: Pearly to greasy
- Streak: White
⚙️ Geological Occurrence
Talc (agalite) typically forms in:
- Metamorphosed ultramafic rocks (soapstone deposits)
- Hydrothermal alteration zones of magnesium-rich rocks
- Associations: Often found with serpentine, chlorite, and carbonates
🏭 Industrial and Scientific Importance
- Paper Industry: Used as a filler to improve smoothness and printability.
- Plastics & Rubber: Acts as a reinforcing filler.
- Cosmetics: Provides softness and absorbency (talcum powder).
- Ceramics & Paints: Improves durability and finish.
- Historical Note: “Agalite” was sometimes used interchangeably with soapstone in industrial contexts.
📖 Conclusion
Agalite is essentially fibrous talc, a name now obsolete but historically used in mineralogy and industry. Today, it is classified simply as talc, the softest mineral, widely used in industrial applications and known for its silky, soapy feel.
In short: Agalite = fibrous talc, an old synonym no longer in formal use.
