What is Vermicultie?

Vermiculite is a natural mineral that expands with the application of heat. The expansion process is called exfoliation and it is routinely accomplished in purpose-designed commercial furnaces. Vermiculite is formed by weathering or hydrothermal alteration of biotite or phlogopite. Large commercial vermiculite mines currently exist in Russia, Africa, China, and Brazil.

When?

Vermiculite was first described in 1824 for an occurrence in Millbury, Massachusetts, USA.

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.

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