Largest Settlements:	Place Population Palagonia 16,227 (2014)

Basaltic breccia.

The locality of Palagonia has given the name to palagonite (Sartorious von Waltershausen, 1853; Des Cloizeaux, 1862), an alteration product around the outer rind of basaltic glasses subjected to the action of water. Its structure and especially its chemical composition vary significantly from one sample to another. There is generally a very distinct border between the pristine glass, or "sideromelane", and the alteration rind; observed by optical microscopy, the latter is characterised by it orange-yellow colouration in natural light and sometimes by slight birefringence in polarized light, while the glass itself is isotropic and honey-coloured. According to recent studies, palagonite may be classified into two broad categories. The first is characterised by an amorphous gel, suggesting to many authors that it results from simple hydration of the glass. In other cases it consists of smectitic clay minerals, crystallized to some extent. Palagonite may form by coprecipitation of glass constituent elements that are initially solubilised, as generally observed for non-zeolitic samples. Palagonite may also form by interdiffusion processes in a residual hydrated glass: this is generally the case for zeolitic samples (Crovisier et al., 1987; Crovisier et al., 2003).


Beside the well-known outcrop at the foot of Monte Caliella, there are other outcrops of volcanics in the municipal territory of Palagonia, but systematic researches for minerals are often prevented by the presence of cultivated lands and highly urbanised areas. Di Franco (1927) described crystals of fluorine-free apophyllite, i.e. hydroxyapophyllite-(K), in basalt cavities in association with "phillipsite" and "herschelite" (presently chabazite-Na). The presence of apophyllite in the Palagonia area, in association with "phillipsite, analcime, and vivianite, was already reported at Contrada Portelle, a disused toponym mentioned by Gemmellaro (1856). Sturiale (1963) described "phillipsite" (now considered phillipsite-Na), epistilbite, "herschelite" (presently chabazite-Na), and analcime from effusive lavas and hyaloclastites evidenced by water well drilling at Contrada Santa Febbronia, about 3 km NE of Palagonia.


NB: The phase which occurres at Monte Caliella is most probably tetranatrolite which in this page is listed as gonnardite.

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