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palagonite Pale yellow to yellow-brown, hydrated, fragmental, basaltic glass, formed by the hydration of metastable hyaloclastite and ion exchange, due to the action of groundwater percolating in the subaerial environment or to the action of sea water in the case of submarine environments. The high surface area to volume ratio of the lapilli-size fragments of glass facilitates efficient chemical exchange with water. Much of the original calcium, potassium, and sodium, and some of the aluminium and silicon, are lost, iron is oxidized, and water is gained. Elements such as iron, titanium, magnesium, and aluminium may be either lost or added. The type locality is at Palagonia, Sicily. Some planetary scientists think that the whole surface of Mars is covered with dust of palagonite origin.