What is VERMICULITE? - Waterproofing Africa, We Reign When It Pours

Its name is from Latin vermiculare, to breed worms, for the manner in which it exfoliates when heated. Associated mineral phases include: corundum, apatite, serpentine and talc. It occurs interlayered with lt chlorite, biotite and phlogopite. It typically occurs as an alteration product at the contact between felsic and mafic or ultramafic rocks such as pyroxenites and dunites. It also occurs in carbonatites and metamorphosed magnesium rich lt limestone

Structure

Vermiculite is a 2:1 clay, meaning it has 2 tetrahedral sheets for every one octahedral sheet. It is a limited expansion clay with a medium shrink-swell capacity. Vermiculite has a high cation exchange capacity at 100-150 lt meq/100 g. Vermiculite clays are weathered micas in which the potassium ions between the molecular sheets are replaced by magnesium and iron ions.