Vermiculite

A mica-like mineral that puffs up when heated, used in potting mixes, lightweight concrete, insulation and fireproofing.

Industrial minerals · No. 71

• Not on a critical list
• HHI 1,754 · moderately concentrated

Flash-heat vermiculite and it swells like an accordion, which is why gardeners and builders use a mineral mined mostly in South Africa.

Chart: Illustration: Vermiculite

Where it comes from

Chart: Map of where it comes from

Vermiculite is a hydrated, mica-like mineral formed when biotite or phlogopite alters, as at Palabora in South Africa. It is mined in open pits and concentrated by screening and air separation.

Three things to know

1. Concentrate is shipped dense and expanded near customers, at 12 US exfoliating plants in seven states.
2. Agriculture takes about 30% of US exfoliated vermiculite, lightweight concrete 16% and insulation 15%.
3. Value depends on flake size, how much it expands and freedom from asbestos; US import reliance is only 25%.

The journey

1. 1 Altered micaBiotite or phlogopite in igneous complexes
2. 2 Open pitMined at sites like Palabora
3. 3 ConcentrationScreening and air separation
4. 4 ExfoliationRapid heating turns water to steam
5. 5 End usesPotting mixes, lightweight concrete, insulation, fireproofing

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