Kimolos is a small island in the southwest Cyclades. Like nearby Melos, it is dominated by volcanic rocks, although there are no records of volcanic activity on the island. The volcanic rocks on Kimolos have been extensively hydrothermally altered, leading to the formation of large deposits of bentonite. These deposits provided for clay-rich sediments which have been exploited for much of the island's history. Kimolian Earth is first mentioned by Theophrastus for degreasing cloth. Clays used in this way became commonly known as fuller's earth throughout Europe; the clay works by absorbing oil and grease. Fuller's earth was also used as a medicine: Dioscorides recorded that it was used in the treatment of tumours and inflammations, and that it had a white or purple hue. The bentonite deposits on Kimolos include deposits of white bentonite (it is usually greenish-grey in hue) and this could be a significant factor in the nature of Kimolian Earth. In addition to the bentonite, the hydrothermal processes affecting the island's rocks have led to the formation of zeolitic tuffs, which are more abundant in the southwest of the island. Zeolitic rocks have a potential industrial application, but are less likely to have had any significance in antiquity. 

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images: view from the small bay near Prassa Kimolos towards Melos; map of Kimolos (from Photos-Jones and Hall 2011).