The paleo-lacustrine diatomaceous deposits of Monte Amiata volcano (Tuscany, Italy) and the Ezio Tongiorgi paleontological collection in the Museum of Natural History of the University of Pisa

At the foothill of Monte Amiata volcano (southern Tuscany, Italy), small extinct lake basins of late Pleistocene age are documented. These lake basins were characterized by the deposition of two very different types of sediment: a) derived from the authigenic precipitation of iron oxides (goethite) and exploited as earth pigments; b) biogenic siliceous sediment composed of fossil diatoms and named diatomaceous earth or diatomite. The lacustrine sediments of Mount Amiata volcano were widely exploited for various applications since ancient times. Literary documents begin in the 16th century, with the descriptions of Cesalpino, Gesner, Agricola, and Imperato. Specific references to the diatomites of Monte Amiata are quoted in the 17th century by Boccone and Bonanno. The quarrying activity was described by Micheli in 1733. During the 18th and 19th centuries, the diatomaceous earths of Monte Amiata are part of the important geological collections of Micheli, Targioni Tozzetti, Baldassarri, Campani, and Tommi. A particular significance has the collection of botanic and ichthyologic fossils collected by Ezio Tongiorgi, and now preserved in the Museum of Natural History of the University of Pisa sited at the Charterhouse of Pisa in the Calci village. These paleontological samples preserve the biological and physical testimonies of the environmental and climatic changes of the late Pleistocene and are now particularly valuable because they are the only remaining evidence of the diatomaceous lacustrine deposits of the paleo-lakes of Monte Amiata. For these reasons, they represent geological materials with a fundamental cultural value.


Introduction
Monte Amiata is a middle Pleistocene [305-231 ka BP; Laurenzi et al., 2015, Laurenzi and silicic effusive volcano culminating at 1738 m above sea level (a.s.l.) located in southern Tuscany (Italy; 43°43'18.84"N -10°31'24.77"E, Figure 1). Monte Amiata activity was dominated by the emplacement of trachydacite and subordinate trachyandesite Landi et al., 2019; and references therein] lava flows and exogenous lava domes, that were produced during two main periods of activity [Principe et al., , 2018 A few years later, the description of a similar earthy material that was found in the territory of the city-state of Siena was reported under the name Agarici fossilis by the Jesuit Filippo Bonanno (or Buonanno;1638-1725, curator of the wunderkammer at the Roman College of the scholar and polymath Athanasius Kircher (1602Kircher ( -1680 [Bonanno, 1709]: "To this is added another earth, which I believe can be understood under the name of white bolus, this earth is very white and very light, and does not dirty the hand in the slightest if touched, braced between the teeth proves to be very juicy like the Samia earth. The use of this earth is very useful against fevers and poisonings. … From the countryside of Sienna, such an earth is found with the name of Agarici fossilis. That is a light, white, crumbly, but not bitter substance similar to Agaric. Thus this agaric was described by Imperato. … The earth so called is similar in its whiteness to lime, but dissimilar in its lightness, which in the Agaric usually is maximum, it is found in the top of caves, with a soft consistency if dissolved in water, it has a fibrous behavior, but finally liquefies like other earths, nor does its origin seem entirely different from the true Agaric, as in the appearance it completely resembles it; it adheres to the tongue, for which reason it feels like the Samian earth and by many physicians is used in its place. It is useful for the repulsions of blood by mouth, and generally in all other things it is used as Samia. Called by some moon's milk, for the whiteness, and tenderness it has, while it is collected in its own places". [Bonanno, 1709] [Bonanno, 1709] The physician Michele Mercati (1541Mercati ( -1593, who was superintendent of the Vatican Botanical Garden under several Popes, in his work Metallotheca Vaticana, written probably between 1570 and 1593 but published posthumous in 1717 [Mercati, 1717], quoted an earth mineral named "Argilla" (clay), coming from the county of Santa Fiora and used in the smelting of precious metals due to its refractory properties: "Argilla … Some are found leaner and some fatter, one that resists fire well, others not at all. The one that resists fire, called by Pliny (33.4) Talc, none like this one tolerates burning breath, flame and matter. This is used by the goldsmith to melt gold and silver, which is located in the county of Santa Fiora not far from the mountain called Laterone, and from other parts of Italy". [Mercati, 1717] "Argilla … Verum alia tenuior reperitur, alia crassior: quaedam ignem fert, quaedam vero minime. Ea, quae fert ignem, Tasconium a [c 33.4] Plinio appellatur; neque enim alia (de Tasconio loquens ait) afflatum, ignemque, & ardentem materiam tolerat. Hae utuntur auri Fabri ad fundendum aurum, atque argentum, quae in Comitatu Sanctae Florae reperitur non longe a monte Laterone vocato, aliisque Italiae locis". [Mercati, 1717] The Florentine botanist Pier Antonio Micheli (1679Micheli ( -1737 in his diary of the Viaggio fatto l'Anno 1733 per diversi luoghi dello Stato Senese (Journey made the year 1733 for different places of the Sienese State; Micheli, 1733;1754a) referred to quarries in the latte di Luna (Moon's milk) near Arcidosso and at Bagnólo (Santa Fiora): "Not far from the aforementioned quarry [at the Bagnora near Arcidosso], there is that of the hard Latte di Luna, that is "Lac Lunae", or a Agaricum fossile or a hard mineral". [Micheli, 1754a] ... "I walked towards the Bagnuolo, ... and when I arrived there I found, just past the last houses below, and on the edge of the chestnut groves, the open quarry of a white, very fine and very light earth, which when chewed does not screech under the tooth, called by Latins Lac Lunae". [Micheli, 1754a] "In poca distanza dalla suddetta Cava [alla Bagnora vicino Arcidosso], vi è quella del Latte di Luna duro cioè "Lac Lunae", sive Agaricum fossile vel minerale durum". [Micheli, 1754a] … "m'incamminai alla volta del Bagnuolo, … e giuntovi trovai, giusto passate l'ultime case di sotto, e a confini de' castagneti, la Cava aperta di una Terra candida, finissima, e leggerissima, la quale masticata non stride sotto il dente, detta da Latini Lac Lunae". [Micheli, 1754a] 5

Diatomaceous earths of Monte Amiata volcano
More than a hundred rock samples collected by Micheli during his 1733 travel at Monte Amiata were part of his private museum in Florence [Vezzoli and Principe, 2020] including two samples of Agarico Minerale or Latte di Luna from Santa Fiora [Micheli, 1754b]. At the premature death of Micheli in 1737, this collection was purchased by his disciple Giovanni Targioni Tozzetti (1712-1783). The private collection of Targioni Tozzetti, including also Micheli's samples, comprised more than 9000 samples of rocks and minerals and was described in a manuscript catalog [Targioni Tozzetti, 1750] (Figure 2).
Giuseppe Baldassarri (1705Baldassarri ( -1785, physician of the main Camaldolese convent of Monte Oliveto Maggiore (Tuscany, Italy), professor of natural history at the University of Siena, and president of the Accademia delle Scienze di Siena detta de' Fisiocritici (Fisiocritici's Academy of Science in Siena), compiled a catalog of natural products that are found in the territory of the city-state of Siena and that are into the private museum of Giovanni Venturi Gallerani [Baldassarri, 1750; http://www.museofisiocritici.it/catalogobaldassarri.asp] (Figure 3a), comprising 130 samples of rocks and minerals, and 37 samples of testacei (fossils). Until 1765, the samples described in the Baldassarri's catalog were exposed in the Museum of the Fisiocritici Academy in Siena as quoted by Targioni Tozzetti [1774], but their current location is unknown. The first mineral product described in this catalog was the diatomaceous earth of Monte Amiata named Agarico minerale following Imperato [1599] (Figure 3b): "1. MINERAL AGARIC, also called Moon's milk; it is found in several places near Castel del Piano, at the foot of the Mount of S. Fiora. ANNOTATION. Called from Gesner Moon's milk, from Agricola Medulla Saxorum, and from Ferrante Imperato Agarico minerale, due to the similarity it has with a mushroom, called Agaric, i.e. Fungus Laricis C. B. Pin. This is a fungal, light, rare, candid, and insipid earth, and can be referred to Marghe genus. It dissolves easily in water, and dyes it white. It has much uses in medicine, and it is attributed the faculty to be refreshing, astringent, and stopping the loss of blood, and the uterine discharges; it is prescribed in tenesmus, and in dysentery with much profit. When pulverized and sprinkles over the ulcers it dries them admirably". [Baldassarri, 1750] "1. AGARICO [Baldassarri, 1750] The Florentine naturalist, agronomist and chemist Giovanni Fabbroni (1752-1822 was among the first to discuss the difference between the various types of earthy mineral materials hitherto united under the names of Lac Lunae (Latte di Luna, moon's milk, guhr), which is a plastic clayey earth, and Agaric (Agarico minerale), which is a calcareous earth, and to underline how the soft, light, and flaky white earth found at Monte Amiata is different from the both.
For this reason, he proposed to name the diatomaceous earth of Monte Amiata as Farina Fossile (fossil flour, bergmehl) [Fabbroni, 1794], and with this name it continued to be locally known since then.
During the 19th century, diatomaceous earth samples from Monte Amiata were comprised in the collection of Giovanni Campani [Campani, 1860] and in the mineralogical catalogs of Cesare Tommi [Tommi, 1890]  . Giovanni Campani was professor of general chemistry at the University of Siena and director of the   in which 528 samples of rocks are described. Among them are three samples of diatomaceous earths from the quarries of Abbadia San Salvatore (Acqua Santa), Castel del Piano (Fonte), and Santa Fiora (Bagnólo) [Tommi, 1890, inventory numbers 222, 383, and 409, respectively;. The Tommi's collection was kept until the first half of the twentieth century at the Chamber of Commerce in Siena, but was subsequently dispersed due to a flooding in the building.
The first hypotheses on the genesis of the diatomaceous earth of Monte Amiata formulated in the eighteenth century suggested that it was the result of the alteration of the Monte Amiata siliceous volcanic rocks (called by the local people as peperino; Vezzoli and Principe, 2020), transported by water and deposited in small depressions [Targioni Tozzetti, 1776-1777Santi, 1795;Tasselli, 1890]. The problem of the origin of this lacustrine sediment was solved by the first modern analyses on the deposits of Santa Fiora basin made by Klaproth [1814], which demonstrated its siliceous chemical composition and proposed the name Kieselguhr, and by Ehrenberg [1836;1838], which recognized its biogenic composition due to siliceous skeletons of Infusoria (including diatoms) ( Figure 5).

Lithological, chemical, and paleontological characteristics
Diatomaceous earths are composed of the fossil microscopic unicellular algae of the Bacillariophyceae class (diatoms), they have an ultra-fine grain size, and are soft and crumbly, with an earthy texture and a pure white color.
Diatoms are microscopic unicellular brown algae, with an internal skeleton, called "frustule", composed of amorphous hydrated silica (opal; SiO 2 • nH 2 O). The average dimensions are between 10 and 200 μm. To develop diatoms need light (for photosynthesis, because they contain chlorophyll) and humidity. They inhabit all aquatic environments: freshwater (springs, streams, rivers, lakes, swamps, and peat bogs), brackish (estuaries), and salty water (seas and oceans). The frustules of the dead diatoms accumulate in large quantities at the bottom of the marine or continental basins, where they remain unaltered and fossilized, forming the deposits known as diatomaceous earth (or diatomite) [Taliaferro, 1933;Cressman, 1962].
Diatomaceous fossils are useful both for biostratigraphy, as based on their evolutionary sequence it is possible to date the sediment in which they are imbedded, and for paleoecology, as they give us indications on the conditions of the habitats of the past. Indeed, they are excellent biological indicators as they are very sensitive to changes in environmental physical parameters such as light intensity, temperature, pH, salinity, and currents velocity, and in chemical parameters such as nutrients (nitrates and phosphates), dissolved oxygen, and abundance of organic matter and silica.
Also the chemical composition of Monte Amiata diatomaceous earths is dominated by silica. The first chemical analysis was that announced by Giovanni Fabbroni in 1791 [Fabbroni, 1794] quoted also by Santi [1795].
The Monte Amiata lacustrine diatomaceous deposits have been described by Clerici [1903a] as a series of alternating white and gray layers parallel to each other, some thick a few decimeters, others thinner than a millimeter ( Figure 6). These layers remained perfectly horizontal in the middle of the lake basin, whereas at the margins they curved following the morphology of the basin coast. Intercalations of thin layers of clay or fine sands are also present. The thickness of the deposit never exceeded 5-6 meters. Monte Amiata diatomaceous earth deposits also contain fossils of fishes and insect, macro-plant remains, pollen, and perfectly preserved large wood fragments.
From the fundamental work of the German zoologist Christian Gottfried Ehrenberg (1795Ehrenberg ( -1876 [Ehrenberg 1836; 1838] on the same sample from the Santa Fiora basin analyzed by Klaproth ( Figure 5), we know that the diatomaceous earth of Monte Amiata is formed almost exclusively by the siliceous frustules of diatoms, with lower concentrations of opal, and impurities such as aluminum silicates (clays), calcium carbonates, and organic matter. Ehrenberg recognized in the sample of Santa Fiora 6 genera and 18 species of diatoms, many of which are still unknown, and among which the Synedra capitata is an exclusive species that forms the main mass of the deposit [Ehrenberg, 1836].
The systematic microbiological analyses that were made by Forti [1899] on samples from the Castel del Piano quarry recognized 12 genera and 35 species of diatoms, all still living today. Other analyses on diatoms were carried out by Clerici [1903a] in the diatomaceous earths of Castel del Piano (La Fonte), Abbadia San Salvatore (Acqua Passante) and Santa Fiora (Bagnólo); by Bradley and Landini [1982] in the diatomaceous earths of the Fontespilli quarry (Bagnólo, Santa Fiora), and more recently by Crawford et al. [2003] in the collection of Ehrenberg's samples preserved in Berlin [Ehrenberg 1836;1838].

Diatomaceous earths of Monte Amiata volcano
on the deposits of a paleo-lake basin of Abbadia San Salvatore (Lame) and by Bertolani Marchetti and Soletti [1972] on the diatomaceous earths of the Fontespilli quarry (Bagnólo, Santa Fiora).
The fossil fishes from the Fontespilli quarry belonging to the Ezio Tongiorgi collection have been studied by Bradley and Landini [1982]. They recognized the species Salmo trutta, Leuciscus cephalus, and Barbus barbus plebejus ( Figure 8). This fossil fauna is contained in the lower part of the diatomaceous deposit, richer in clay and organic matter. The specimens generally appear as imprints of the skeletal structure, the fossilized bones are almost totally missing, and the soft parts are preserved as a carbonaceous patina. This indicates that burial and fossilization took place in a reducing environment, poor in oxygen, and devoid of necrophagous organisms [Bradley and Landini, 1982].

The industrial production
Diatomaceous earths have been used at least since the eighteenth century as abrasive to clean metals, as building material, and as medical remedy [Baldassarri, 1750;Santi, 1795]. Subsequently, this material was used for several other applications. Fabbroni (1794] thought of making floating bricks, and Campani [1865] suggested using it for the preparation of soluble alkaline silicates. At the beginning of the nineteenth century, with the advent of industry, the diatomaceous earths (in German kieselgur, bergmehl = fossil flour, or kieselschaale = diatomite) were used for industrial applications after their accidental discovery during a well drilling in Lower Saxony (North Germany). An important pulse for a massive extraction of this material, all over the world and also at Monte Amiata, was given by Alfred Nobel's dynamite discover in 1867 and by the consequent use of diatomaceous earths as a stabilizer of nitroglycerin.
Diatomaceous earths have a great economic importance because of their physical characteristics: they are microporous (they can absorb up to 3 times their weight in water) and chemically inert in many liquids and gases, and have very low density (0.32-0.64 kg/l against 1.00 kg/l of water), a very homogeneous composition (containing 80-95% of silica, SiO 2 ), low thermal conductivity, and high melting point (1000-1750°C). Currently uses of diatomaceous earths are as filter in enology or for drinking water, abrasive for polishing soft metals, insulator in construction and in ceramics, and absorbent in the preparation of soaps and in particular chromatographic analyses.
At Monte Amiata, quarry cultivation was carried out by cutting the mineral deposit into parallelepipeds on a front comprising all its thickness, and proceeding by progressive cuts, so that the waste went to fill the void left by the removal of the blocks previously cut [Clerici, 1903a;De Castro, 1914]. Diatomaceous earths were extracted wet, placed to dry in the air under shelters, disintegrated and sieved, and finally packed in bags.
Transportation was by rail from the Monte Amiata Scalo station, located on the valley of the River Orcia about 5 km north of Castel del Piano. Two commercial qualities of diatomaceous earths were distinguished, based on color and purity, a very white with a density of 0.08 g/cm 3 and a light green with a density of 0.30 g/cm 3 [Clerici, 1903a]. A technical improvement concerned the use of drying ovens, which allowed the reduction of the residual water content from 30% to 5%.

The Fontespilli basin
The lake deposits of diatomaceous earths of Fontespilli (Bagnólo, Santa Fiora) were those most affected by the exploitation activity and those most studied from a geological point of view, due to their extension and mineral abundance. Presently, the area affected by the mining activity is occupied by various artisan and residential settlements, but the depressions of the two main quarry areas are still visible, bounded towards the mountain by slopes of 3-4 m height corresponding to the ancient quarry fronts (Figure 9). No diatomaceous materials are possible to found in these areas nowadays, as all the strata of diatomaceous earths have been completely removed during the past mining activity .   14 Figure 10. The stratigraphic log of the excavation front of the Fontespilli quarry (Bagnólo, Santa Fiora), redrawn from Blanc and Tongiorgi [1937].

Paleoenvironment and evolution of the paleo-lakes of Monte Amiata
Both in the case of earth pigments and diatomaceous earth, the purity and very fine grainsize of the minerals indicate that during the sedimentation process the contribution of terrigenous pollutants, deriving from erosion and runoff of detrital materials on the slopes of the volcano, was practically absent in the lake basins. This fact, besides favoring a permanent clearness of the water, indirectly suggests the concomitance of a relatively warm and little rainy climate and the development of a thick vegetation mantle to protect the soil. In fact, the fossil remains of macrophytic plants, which lived around the basins, testify to a covering of mixed mountain vegetation of broadleaved and coniferous trees in a period of temperate-warm climate with a prominent oceanic character [Blanc and Tongiorgi 1937;Tongiorgi 1938Tongiorgi , 1939.
The feeding of the basins could take place above all from springs. The water of the springs had to be strongly mineralized with iron oxides and/or colloidal silica to provide respectively the raw material for the deposition of limonite/goethite in the case of earth pigments, or for the development of diatoms in the case of diatomaceous earth. If in some cases we can hypothesize the presence of real lake basins, such as in Bagnólo (Santa Fiora), probably in others cases it was just marshy areas or encrustations around mineralizing springs, such as the Lame and Acqua Santa (Abbadia San Salvatore), or pools of limited extension above the surface of lava flows, as in Piancastagnaio.
The stratigraphic sequence of the sediments that made up the filling of the main lacustrine basins (Figure 10) gives us indications on the succession of different lithologies and therefore on the evolution over time of the geological and environmental dynamics [Lotti 1910;Blanc and Tongiorgi 1937]. Abundant vegetal, ichthyologic, and entomological remains have been found both in the peat and diatomaceous layers [Forti, 1899;Blanc and Tongiorgi, 1937;Bertolani Marchetti and Jacopi, 1962;Bertolani Marchetti and Soletti, 1972;Bradley and Landini, 1982] and indicate some changes in ecological conditions. The reconstructed evolution of these paleo-lakes includes a first phase in which there is deposition of clays and iron oxides, as in the deposits of Bagnólo (Santa Fiora), Caselle and La Sega (Castel del Piano). The paleontological analysis indicates for this initial phase conditions of cold climate due to the predominant presence of Pinus, with Picea and Betula [Clerici, 1903b;Lotti, 1910;Blanc and Tongiorgi, 1937;Bertolani Marchetti and Soletti, 1972].
During a second phase, the lower diatomaceous layers were deposited, with contamination of terrigenous material and abundance of organic matter [Bradley and Landini, 1982]. These diatoms layers are characterized by an oligotypic association of the planktonic genus Ciclotella and very few benthic diatoms. The sedimentation environment that can be reconstructed for this second phase is that of a lake sufficiently large and deep (15-20 m) to accommodate typical limnetic forms [Forti, 1899], with a bottom below the photic zone and poorly oxygenated [Bradley and Landini, 1982]. The water was not clear due to the suspended terrigenous material and the abundant production of phytoplankton. The fishes lived in the intermediate-shallow zone. The climate was continental warm with great development of Fagus, Abies, and Castanea [Tongiorgi, 1939]. Relatively cooler and drier conditions were suggested by the presence of Pinus, Betula and Carpinus into the thicker peat layer interstratified with diatomites at Bagnólo (Santa Fiora) and Lame (Abbadia San Salvatore) [Bertolani Marchetti and Jacopi, 1962;Bertolani Marchetti and Soletti, 1972].
In a third phase, a climatic change induces an increase in temperature, but not an increase in water influx, with related absence or scarcity of meteoric precipitations. This fact leads to initially optimal environmental conditions for the proliferation of diatoms within a clear water body. Moreover, the relatively high concentrations of dissolved silica generate conditions close to saturation in opal, which further promotes the growth of diatoms. However, the gradual loss of water by evaporation causes the depth of the lake to be reduced to a few meters, turning it into a pool of algae covered with epiphytic diatoms [Forti, 1899). The environment is no longer favorable to the community of fishes, which die in mass. With the end of the evaporation process also the diatoms die and settle down to the bottom of the almost dried up basin, generating the layers of pure diatomite, white and powdery, consisting of predominantly benthic diatoms, such as the genus Frigilaria [Bradley and Landini, 1982], contrary to what happened in the second phase of paleo-lake evolution in which planktonic diatoms prevailed.
The pollen remains of Pinus in the highest part of the diatomite sequence indicate the transition to cool and wet climate [Bertolani Marchetti and Soletti, 1972] that foreshadows the cold-climate peak characterizing the overlying sedimentary complex that represents the fourth phase. During this last phase, the lake deposition is interrupted, simultaneously in all basins, by a complex of sediments composed of alluvial volcanoclastic sands and gravels, with intercalations of clays and peats (Figure 10) [Blanc and Tongiorgi, 1937]. These sediments are generally sterile of fossil remains. The sudden change of sedimentation style suggests a considerable and general change in the feeding regime of the basins, which can be interpreted as the effect of having arrived a cold and rainy climate [Blanc and Tongiorgi, 1937]. This climatic variation has had as consequence a thinning of the vegetation surrounding the basins, colder temperatures, a more active thermo-clastic breakup of the rocks, an intense and widespread runoff on the slopes, and the increase of waters turbidity.
Finally, the younger sediment complex is represented by sands and silts more or less rich in organic matter (even coals fragments deeply altered in soil), and by vegetable soil (Figure 10). It indicates a scarce colluvial and alluvial sedimentation with a substantial stability of the topographic surface that has favored the development of intense processes of weathering.

Age of lake deposits and relations with the volcanic activity of Monte Amiata
In order to define the age of the lacustrine deposition of earth pigments and diatomaceous earths of Monte Amiata, and their relationship with volcanic activity, we can use geological, paleontological, paleoenvironmental, and archaeological tools.
All previous authors agree in considering the formation of lake basins as a phase completely subsequent the activity of the Monte Amiata volcano [dated at 305-231 ka by Laurenzi et al., 2015, Laurenzi and.
On the basis of the thickness (about 11.5 m) of diatomite strata in the quarry of Fontespilli (Bagnólo, Santa Fiora) and the mean thickness (1-3 mm) of laminae (equated to varves) that compose it, Fornaca Rinaldi [1968] formulated the hypothesis that the duration of the environmental conditions in which it was possible to form the diatomaceous deposits of Monte Amiata was of about 20,000 years. The only radiometric age available on the Monte Amiata lake deposits is that performed by Fornaca Rinaldi [1968] with the 230 Th 238 U method on the diatomaceous deposit of Fontespilli (Bagnólo, Santa Fiora) which provided an age of 130-140 ka before present.
From the stratigraphic point of view, the lake deposits of Monte Amiata are superimposed on the trachydacitic lavas belonging to the first phase of activity of the volcano . There are no direct geological relationships between the lake deposits and the volcanic products of the second, most recent, phase of activity , due to their different areas of distribution. However, the lake deposits are never covered by primary volcanic units, but only by later alluvial or colluvial volcanoclastic deposits derived from the exogenous weathering of volcanic rocks.
From the paleontological point of view, the fossil species of diatoms, macrovegetation and fauna found in Monte Amiata paleo-lake sediments are identical to those currently living.
From the paleoenvironmental and paleoclimatic point of view, the main phase of Monte Amiata lacustrine sedimentation refers to a period of temperate-warm climate with a prominent oceanic character bordered, both at top and bottom, by deposits evidencing a colder and wetter climate [Blanc and Tongiorgi, 1937;Tongiorgi, 1938;1939]. This period of temperate-warm climate possibly corresponds to the last interglacial period [the Eemian or Marine oxygen Isotope Stage MIS 5e; Regattieri et al., 2016], which developed between 140-130 ka and 115-110 ka before present [Adams et al., 1999;Shackleton et al. 2003;NEEM, 2013] in agreement with the age of 130-140 ka of the sediments and a lifetime of 20,000 years of the lacustrine basins suggested by Fornaca Rinaldi [1968]. The end of the lake sedimentation and the beginning of the alluvial progradation is attributable to the intervention of a colder climate coinciding with the beginning of the last glacial period at about 115-110 ka BP. Subsequently, during the last phase of colluvial sedimentation and pedogenesis, the presence of Fagus and Picea carbons gives us testimony of the vegetation corresponding to the return to an oceanic climate, occurred with the current postglacial period at 14 ka ago [Tongiorgi, 1938].
From the archaeological point of view, within the lacustrine sediments any lithic industry is absent; while in the overlying alluvial layers the archaeological findings are significant. D'Achiardi [1872] reported the findings in the Mazzarelle quarry (Castel del Piano) of artifacts (scraper and arrows) and flint and jasper shards, in the lower part of the alluvial deposit, and of objects in bronze or copper in the upper part. In the Caselle quarry (Castel del Piano), worked oak poles, probably of huts, were found on the surface separating the diatomaceous earths from younger volcaniclastic debris [Blanc and Tongiorgi 1937]. According to Grifoni Cremonesi [1971] other archaeological artifacts (such as polished stone axes, arrow cusps, copper axes and small daggers, bronze axes, bronze age ceramics) were found in the diatomaceous earth quarries of Castel del Piano (Campogrande and Caselle), and Santa Fiora (Bagnólo) [Sestini 1934[Sestini , 1936Blanc and Tongiorgi 1937], without the description of a precise stratigraphic position, and are preserved in the Archaeological Museums of Rome, Siena, Perugia, and at the Luigina Vezzoli et al.

Diatomaceous earths of Monte Amiata volcano
University of Pisa. In summary, at the contact with the diatomaceous deposits, in the deeper alluvial layers, there is a typical industry of the Middle Paleolithic [Mousterian; lasted roughly from 160 ka to 40 ka BP in Europe; Shaw and Jameson 1999]. An Upper Paleolithic industry follows towards the top of the alluvial and peaty sediments. In the uppermost layers a Neolithic and Bronze Age industry was found accompanied by a rough ceramic, with abundant remains of fireplaces containing Fagus and Abies coals [Tongiorgi 1938]. Born on March 12, 1912 in Milano, Ezio Tongiorgi [https://siusa.archivi.beniculturali.it;Alabiso and Tongiorgi, 2010] was student at the Scuola Normale Superiore and at the University of Pisa, where he graduated in Natural Sciences in 1934 ( Figure 11). After few years as assistant at the Botanical Institute of the University of Pisa, in 1938 the research carried out on the history of the vegetation of the Apennines earned him the prize of the Società Italiana per il Progresso delle Scienze, and in 1939 he obtained the qualification for the university teaching.

Ezio Tongiorgi (Milano 1912 -Pisa 1987) -biographical notes
At the end of the Second World War -during which he served as a second lieutenant in artillery, before moving into the ranks of the Roman Resistance -Tongiorgi resumed his scientific activity at the Botanical Institute of Pisa University first as assistant, then as director of the Istituto e Giardino Botanico.
In the following years Ezio Tongiorgi gradually expanded his fields of interest from botany to paleobotany, from anthropology to paleontology, from nuclear geology to scientific museology. In these areas he promoted numerous  The need to accurately date the archeological finds from Grotta del Leone led Tongiorgi to the creation, in 1958, of a pioneering laboratory of nuclear geology (Laboratorio di Geologia Nucleare) in the framework of the Italian Consiglio Nazionale delle Ricerche (National Researches Council -CNR for short), that becomes a very advanced research center frequented by scientists from all over the world. It is here that the first Italian mass spectrometer instrument was built, for dating ancient artifacts through the analyses on the decay of 14 Carbon isotope [Ferrara et al., 1959]. Tongiorgi was the first director of this Institute and in 1965 became also full professor of nuclear geology at the University of Pisa. The Laboratory of Nuclear Geology was transformed during the 1980s into the CNR Institute of Geochronology and Isotope Geochemistry (Istituto di Geocronologia e Geochimica Isotopica), that in turn during the 2010s merged with another CNR scientific institution created by Ezio Tongiorgi, the International Institute for Geothermal Researches (Istituto Internazionale di Ricerche Geotermiche), to form the present Institute of Geosciences and Earth Resouces (Istituto di Geoscienze e Georisorse).
Considering the importance of Italian geothermal resources for the production of electricity, starting from 1966, Ezio Tongiorgi promoted the formation of a group of expert CNR researchers, which in 1969 resulted in the establishment of the International Institute for Geothermal Research based in Pisa and of which he was the first director. As part of this Institute, periodic international courses of specialization in geothermal energy were held in the 1970s for researchers coming from developing countries. As a matter of fact, the ruling class of the institutions involved in the research and development of geothermal energy in Latin America in the following decades has all passed through this school. In 1972, Tongiorgi started the still existing "Geothermics" scientific journal.
As an application of his interest in Earth Sciences to the cultural heritage, Ezio Tongiorgi applied also to the study of ancient pottery (in particular the medieval earthenware bowl inserted in the facades of many of the Romanesque

The Museum of Natural History of the University of Pisa inside the Charterhouse of Pisa in Calci
The Charterhouse of Pisa in Calci ( Figure 12) is a vast monumental complex that rises on the slopes of Monte Pisano, a few kilometers from the city of Pisa. It was a cloistered monastery of the Carthusian order of San Bruno Luigina Vezzoli et al.

Diatomaceous earths of Monte Amiata volcano
founded in 1366 at the behest of the Archibishop of Pisa Francesco Moricotti and thanks to the financial support of illustrious Pisa families. The convent assumed also a political importance, in particular after the annexation of the ancient Benedictine monastery of the island of Gorgona, which took place in 1425. It was suppressed first in the Napoleonic era, and then by the Savoy, but it was once again inhabited by the monks until 1969 when they definitively abandoned it. It was enlarged between the seventeenth and eighteenth centuries and today is a splendid baroque monument set in a highly suggestive landscape ( Figure 12). It is following the foundation of the monastic complex that the Calci valley, originally called "dark", was renamed Val Graziosa ("full of grace" valley).
After the last monks abandoned the Charterhouse complex, Ezio Tongiorgi did his utmost to ensure that the prestigious monumental building was entrusted to the University of Pisa in order to establish a Museum of Natural  The Naturalistic Gallery of Pisa, the initial nucleus of the Museum, was established in the late 16th century as part of the Botanical Garden. In 1814, the Gallery became independent of the Botanical Garden, and, in the late 19th century, its naturalistic collections were divided into three separate museums: the Museum of Zoology and Comparative Anatomy, the Museum of Geology and Palaeontology, and the Museum of Mineralogy and Petrology [Landini, 2011]. The Second World War marked the beginning of a phase of decline and isolation that ended when the three museums were rejoined and relocated into the Charterhouse of Pisa in Calci in the late 1970s.
A Centre for Environmental Education (CEA) was established in 1997, and since 2008 the museum has assumed the role of "Hub of Environmental Education" for the Pisa area. Various institutions promoting the cultural and scientific dissemination have their headquarters at the Museum of Calci. The exhibitions have been expanded with new galleries and the services to the public have been improved [Landini, 2011]. Today the Museum offers also temporary scientific exhibition in addition to the permanent ones based on both historical and recently acquired specimens.

The paleontological collection
The The ichthyologic specimens include all those published by Bradley and Landini [1982] and referred to Salmo trutta (Figures 8a, 8b and 8c) and Squalius cephalus [named Leuciscus cephalus in Bradley and Landini, 1982] ( Figures 8d and 8e), in addition to 30 specimens extremely fragmentary but that, to a first examination, appear to be comparable to the species already reported. The fauna is completed by two teeth referable to carnivores. In the collection are also some sediment samples, the most interesting being: a series of samples of diatomite in continuous stratigraphic succession for a total thickness of about 45 cm, a sample of diatomite with evident lamination (Figure 6), a glass ampoule with diatomite powder, a clay sample with a partially unreadable note referring to the locality "Pratucci", and a partially consolidated coarse sediment.

Diatomaceous earths of Monte Amiata volcano
All the published ichthyologic specimens, as well as the other sufficiently complete fish remains, have been catalogued individually. On the contrary, only the most significant plant specimens have been given an individual inventory number; while for the others, pending a specialist study, a cumulative inventory number has been attributed to each of the original boxes in which the material reached the museum (labeled as belonging to the old "Institute of Human Paleontology of the University of Pisa"), for each boxes the number of specimen is reported.
The photographs and a summary descriptive table of the inventoried paleontological samples of the Tongiorgi collection are available on the website of the Tuscany Region: https://www.regione.toscana.it/-/documentazionerelativa-al-volume-il-vulcano-di-monte-amiata.

Concluding remarks
The extinct lacustrine basins at the foothill of Monte Amiata volcano have been the place for the exploitation up to the exhaustion of the diatomaceous earth and earth pigments here sedimented during the late Pleistocene. Both the earth pigments and diatomaceous earth deposits are closely related to the high availability of colloidal silica and ferrous solutes from low temperature hydrothermal springs draining the volcanic edifice. The age of the lacustrine sedimentation (140 -130 ka) is consistently younger than the volcanic activity of the Monte Amiata volcano (305 -231 ka).
Diatomaceous earths represented a richness of this territory, and experienced different uses during centuries, but from the geological point of view they were the witnesses of the evolutive history of Monte Amiata lacustrine basins. This history has been reconstructed on the basis of the previous geological and paleontological studies and can be summarized in a number of sedimentation episodes mainly driven by climatic changes: 1) The first phase is represented by the sedimentation of clay and iron hydroxides in well-developed lacustrine basins, during cold climate conditions, as suggested by the pollen predominance of Pinus, Picea, and Betula.
2) During the second phase, the sedimentation of the diatomaceous earth begins. The abundant plant, ichthyologic, and entomologic fossils indicate a warm continental climate with great development of Fagus, Abies, and Castanea. The lithological and paleontological characteristics of the diatomaceous earth suggest a gradual drying of the lake and the final transition to a humid fresh climate. The quite significant thickness and the purity of the deposit are due to the environmental situation of the lake basins. It has probably remained stable for hundreds or thousands of years to allow diatoms to develop exclusively, continuously, and without polluting of terrigenous sediments.
3) The third phase is characterized by the simultaneous end of the lacustrine deposition in all the basins. Its upper limit is coincident with the end of the last inter-glacial period (at about 110-115 ka ago). The alluvial sedimentation of volcaniclastic sands and gravel is the result of a sharp environmental change that is interpreted as the effect of a climate change and the establishment of cold and rainy conditions.
4) The last stage shows a low colluvial and alluvial sedimentation with a substantial stability of the topographic surface until the present times.
The diatomaceous earth of Monte Amiata and its fossil content have been the subject of important geological collections during the eighteenth and nineteenth centuries: Micheli [1733], Targioni Tozzetti [1750], Baldassarri [1750], Campani [1860], and Tommi [1890]. They also constitute the paleontological collection formed between 1953 and 1956 by Professor Ezio Tongiorgi, now preserved in the Museum of Natural History of the University of Pisa.
The Tongiorgi collection consists of: 386 plat remains, 61 ichthyologic speciments, 2 mammalian teeth, and 5 samples of sediment. The fish remains were deposited in the museum after their publication by Bradley and Landini [1982], who recognized the living species Salmo trutta and Squalius cephalus, while all the other materials arrived around 2010. Among plant remains, the numerically dominant element of the collection, different types have been recognized: leave impressions, wood fragments, branch impressions, conifer's cones or their moulds, and several coal pieces but a detailed study of this material is still pending.
These paleontological samples represent the biological and physical testimonies of the environmental and climatic changes of the late Pleistocene and are now particularly valuable because they are the only remaining evidence of the ore deposition occurred in the lacustrine sediments of Monte Amiata. For these reasons, they represent geological materials with a fundamental cultural value and merit to continue to be accurately preserved and better known.