Vermiculite

Characteristics and Occurrence of Vermiculite

• First described in 1824 in Millbury, Massachusetts
• Formed at the contact between felsic and mafic or ultramafic rocks
• Found in carbonatites and metamorphosed magnesium-rich limestone
• Associated with minerals like corundum, apatite, serpentine, and talc
• Interlayered with chlorite, biotite, and phlogopite
• 2:1 clay structure with limited expansion and medium shrink-swell capacity
• High cation-exchange capacity at 100–150 meq/100 g
• Weathered micas with potassium ions replaced by magnesium and iron ions

Commercial Uses of Vermiculite

• Molded shapes: used in aluminum smelting industry, open fireplaces, and high-temperature insulation
• Calcium silicate boards: added to slurry for heat-cured boards
• Brake linings: utilized in automotive brake linings for thermal resistance
• Roof and floor screeds, insulating concretes: added to Portland cement for lightweight, insulating concrete
• Soilless growing medium: combined with peat for horticulture, promotes faster root growth
• Seed germination, root crop storage, soil conditioner, loose-fill insulation

Fire Protection and High-Temperature Applications

• Vermiculite board for fireproofing ductwork, additive to fireproof wallboard
• High-temperature coatings, firestop coatings, barrier coatings for films
• Vermiculite dispersions, binders for construction materials, oxidation-resistant coatings
• Waste treatment: cation exchange capacity for fluid purification, pollution control
• Others: packing material, substrate for animals, lightweight aggregate for plaster

Commercial Manufacture and Global Production of Vermiculite

• Top producers: South Africa, Brazil, US, China
• International trade association: The Vermiculite Association
• Exfoliated vermiculite production, blending with perlite, varied end products
• Specialized end processors in various industries

Health Concerns, Alternatives, and Related Concepts

• Asbestos: carcinogenic fibrous silicate mineral, banned in many countries
• Coir: natural fiber from coconut husks, environmentally friendly alternative
• Expanded clay aggregate: lightweight aggregate for horticultural applications
• Fireproofing: process to enhance fire resistance in buildings
• Firestop: sealant to prevent fire spread, essential for fire barrier integrity.

Vermiculite Data Sources