|
 Risorse Ambientali |  Mineralogia ed attività minerarie | MINERALOGY AND MINERAL ACTIVITIES
The great variety of minerals found in the territory of Val di Cecina is mainly linked to three fundamental elements: 1. Presence of ophiolite rocks rich in copper,  magnesite, calcedony, manganese. 2. Evaporites (rocks formed with the evaporation and drying up of lacustral or sea basins) linked to the geological phase of the “Lake-Sea” of miocene which brought to the formation of rock salt and alabaster. 3. Endogenous phenomena linked to the intrusion of surface magma in the geothermal area.
We must begin with a general consideration: Val di Cecina, with regards to metalliferous minerals, has been described as "rich of poor deposits", which properly reflects the current situation, except for the rock salt. The extreme variety of rocks and minerals led to the exploitation of the mineral resources of Val di Cecina since the Etrurians. Sure evidences date back to 974: from the historical archives, it is possible to trace back the extraction of rock salt and the evaporation process carried out in specific sheds through lead boilers, called “Saline per ottenere, tramite la loro evaporazione, il sale.')" onMouseOut="toolTip()"> moie”. With the Medici family, a prolific investigation process for the search of copper begins: this marks the beginning of the extraction activities which is still carried out today by renowned figures such as for example Larderel.
With regards to copper, the only important extraction centre has been Montecatini Val di Cecina in the past. Deposits already known during the Etrurian age, saw a first extraction phase between 1562 and 1630 with Cosimo I; later on, extraction resumed successfully only in 1827, until Montecatini became the biggest copper mine in Europe. Works were suspended in 1907 until it was finally closed in 1963, due to the exhaustion of the deposit. Other mines, with less luck, were opened throughout Val di Cecina: Libbiano, Micciano, Miemo, Montecastelli, Botticella, Rogheta are only some of the areas involved in extraction activities in the past.
Among the minerals that were a resource in the past, we find first of all magnesite: this is a mineral general associated to serpentiniti, used in the production of refractory materials or as decorative stone, commonly known as onyx. In Val di Cecina, deposits are located in Poggio Castiglione in the Natural Reserve of Monterufoli-Caselli, San Dalmazio, Monterufoli and Miemo.
Calcedony based minerals and opals are used as decorative stones: those extracted from Monterufoli and Caselli, which are colourful, have been extensively used in Medicean Florence, by Hard Stones Factories.
The lacustral sediments of Upper miocene (sediments formed inside lakes) brought in the past to the extraction of lignite, mainly used as fossil fuel: along torrent Ritasso in the Natural Reserve of Monterufoli-Caselli, the remains of the railway that was connecting Casino di Terra with Villetta di Monterufoli station up to 1928 are still visible, which was used to load lignite from the mine, where the factory of Villetta is now located.
But the most obvious wealth, which is still extensively exploited, consists in the piles of rock salt, which origin dates back to the "Lake-Sea" phase of miocene. The favourable conditions of the deposit of alabaster and then salt occurred between 6 and 7 million years ago during the messinian stage, in an environmental context characterised by marginal sea basins which were precariously linked to the open sea, where the salt rate could become so high to favour not only the deposit of gypsums and rock salt, in extremely peripheral basins. The rock salt is found in amygdale masses, so defined for their particular shape, inside dark clays, alternated to sands and marlstones. The main deposits are located near the Salt mines of Volterra, Ponteginori, Buriano and Querceto. They are mainly used in the food industry, thanks to the high quality of the extracted salt, and they are also used as industrial raw material for the production of sodium carbonate.
The alabaster, a dehydrated calcium sulphate, is also linked to the presence of gypsum deposits of the evaporation stage. It is still used mainly for decorative purposes: due to the fact that it is easy to work with, it has been extracted since the times of the Etrurians and the crafts of Volterra are famous all over the world. Nowadays only.....................are open, but there are still numerous active laboratories. |
|
 This text is also
available in English Language
 Mineralogia ed attività minerarie | |
|
|
|
|
|
|
|
|
