Terminology

• Exfoliated vermiculite: expanded by heat
• Libby vermiculite: from the Libby, Montana mine, contaminated with asbestos
• Cation-exchange capacity: 100 to 150 meq/100 g

History and demand

Sourcing

• 2014: South Africa, Brazil, the US, and China held about 90 percent of mined output
• 1920s: the Libby mine in Montana began; W. R. Grace acquired it in 1963; operations stopped in 1990; it may have supplied about 80 percent of world vermiculite

Composition and production

Raw materials

• Formed by weathering or hydrothermal alteration of biotite or phlogopite

Properties

Physical

• Mohs hardness: 1.5 to 2
• Specific gravity: 2.4 to 2.7 unexfoliated; 0.065 to 0.130 exfoliated (about 4 to 8 lb/ft3)
• Molded shapes: heat cured at up to 180°C for up to 24 hours; service temperatures up to 1,150°C

Uses in buildings

Building elements

• Wall and Roof Insulation: loose-fill insulation for masonry and block
• Fire-Rated Assemblies: aggregate for spray fireproofing and wallboard additive

Pros and cons

Pros

• Very light when exfoliated
• Service temperatures up to 1,150°C in molded shapes

Cons

• Older stock may contain asbestos
• Libby mine contamination led to over 400 deaths and a US EPA public health emergency in 2009

Sustainability

Health

• Government estimates put vermiculite insulation in more than 35 million US homes
• EPA spent $120 million in Superfund money at Libby; W. R. Grace paid $54.5 million in fines

Sources

• Wikipedia: Vermiculite, https://en.wikipedia.org/wiki/Vermiculite
• Wikimedia Commons: Vermiculite1.jpg, photo by KENPEI (CC BY-SA 3.0), https://commons.wikimedia.org/wiki/File:Vermiculite1.jpg