Vermiculite was first described in 1824 for an occurrence in Millbury, Massachusetts. Its name is from Latin vermiculare, "to breed worms", for the manner in which it exfoliates when heated.
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 limestone. Associated mineral phases include: corundum, apatite, serpentine, and talc. It occurs interlayered with chlorite, biotite and phlogopite.