THE following three Indian vermiculite samples: (i) Bagespura, (ii) Malavanghatta and (iii) Hazaribagh have been examined by X-ray and differential thermal analysis. The samples are of flaky habit and exfoliate on heating. All the samples give a basal reflexion of 14 Å, which collapses to 9.6 Å on heating to 750°C. In the differential thermal analysis curves (Fig. 1) there are two sharp water-loss peaks at 150°and 250°C, similar to true vermiculites. In each of the samples (i) and (ii) there is an additional endothermic peak at about 100°C, perhaps due to absorbed water. In all the samples there is an endothermic peak near 900°C. © 1962 Nature Publishing Group.