Since 2004 the School of Medieval Archaeology at Siena University has been carrying out an archaeological survey on the territory of Monterotondo Marittimo. The aim is to define the diachronic settlement tendencies and at the same time clarify the role played by the exploitation of the natural resources present in the area, in particular those below ground. In fact, the territory in question is rich in mixed sulphates and alunite. In the area of Monteleo-Macchia dei Burelli in particular, topographical analyses identified substantial evidence for the production of alum, known from documents from the 18th century onwards. More specifically, quarry faces, bore holes and tunnels still usable in part were found. Close to the quarry three distinct sets of ovens with different structures were identified. Over all the site, where the Lorraine Regency made conspicuous investments from the mid 18th century, which was not touched after the cessation of production activities which functioned between 1741 and 1753, is of unique importance for the study of the techniques for producing alum from alunite in the pre-industrial period. Moreover, the historical documentation is greatly advantaged by the fact that in 1745 Monteleo was visited by Giovanni Targioni Tozzetti, who stayed there for seven days observing the work of the “alluminotti” and wrote detailed descriptions of his findings for the Count of Richecourt. During September-October 2008 the department of Archaeology and History of Art began the first excavations of the complex. The aim was to define its layout and, in particular, study two of the four ovens near the large quarry of Buca dei Falchi. Overall the ovens were in a good state of preservation and showed the traces of numerous repairs connected with the firing phases. As well as permitting a correct reading of the functioning of these structures within the alum production cycle, the data which emerged at the end of the investigation also led to the hypothesis that the first phase of use of the alum mine at Monteleo dated back to at least the 16th century, that is the period of the first great resumption of Tuscan alum production following the fall of Constantinople in 1453.

During September and October 2009 the University of Siena’s School of Medieval Archaeology carried out a second excavation campaign on the site of Monteleo, extending the 2008 excavation area. By the end of the season two of the four kilns were completely excavated, whilst a third was only partially so. The archaeological data provided information regarding the structures’ function and chronology. The first of the two excavated structures (Kiln 1) was certainly for lime production. The kiln, whose internal stratigraphy was completely removed, had a maximum diameter of 3.58 m, interior diameter of 2.50 m and was 3.18 m deep. Inside the kiln, deposits containing charcoal and ash were bordered by a series of simple structures, defined as “spallette”, thought to have served as an aid to the stacking of the materials to be fired. The excavation of kiln 2, overall depth 2.90 m, foresaw the removal of the rubble layers resulting from the structure’s abandonment, below which were levels of ash, charcoal and stones. These layers were cut by the construction of a brick-built offset, already uncovered by the 2008 excavations, at 1.66 m below ground level. The presence of such a structural element, which did not show any significant alterations caused by exposure to high temperatures provided important evidence for the function of this structure. In fact, this type of element is not attested in lime-kilns, whilst it would be more in keeping with the leaching process, during which large metal cauldrons were inserted into the furnaces, supported on particular housings. This hypothesis, also supported by a comparison with other known structures, would also explain the lack of alteration in the bricks forming the offset, as the temperatures reached by leaching kilns are much lower than those necessary for the calcination process, which occurred at between 500° and 600°. The excavation was extended to the third kiln structure, which was dug to a depth of 2.15 m. Inside the kiln a number of pottery vessels, some intact, came to light. They had been leant on the brick offset in a late phase when the structure was no longer used as a kiln. The assemblage was quite rich and comprised closed forms (slipped flasks, glazed cooking pots) and open forms (large marbled plates, enamelled bowls, glazed casseroles), productions that were circulating in the area between the 16th-17th century. This pottery dated the end of the kiln 3’s productive phase to during the 15th century. The new excavation data, in particular that regarding the diverse kiln typologies, together with the dating from the pottery found in kiln 3, confirms what was hypothesised in the previous year. It also showed that these were not 18th century late grand-ducal structures, as described in the well known text written by Targioni Tozzetti, dating to 1754, rather these structures were what remained of the earlier alum mine founded by Rinaldo Tolomei at the end of the 15th century.

In June-July and Septembre-October 2010 the excavation of the four kilns situated next to the Buca dei Falchi was completed. The investigation was extended to the area next to the road, where the building of the 18th century alum mine stood. It was thought that structures for water supply and regimentation necessary for the alum producing operations were situated in this zone (channels and cisterns). The excavation showed the existence of channels but brought to light evidence of a system comprising at least three productive structures, as yet of uncertain interpretation, with the exception of a “boiler” used during the leaching of the product and belonging to the type described in 16th century technical manuals. The four kilns which were completely excavated were certainly originally created for torrefacation. However, the history of this Renaissance company, although shortlived (the exploitation was exhausted between 1507 and 1508) had its ups and downs and the productive structures were radically renewed on at least one occasion. The kiln excavations found evidence for the drastic reorganisation of the installations, one of which ended up as a coal store (kiln 4) and another as a storecupboard (kiln 3). The function of kiln 1 remained substantially unaltered throughout its use. On the contrary, kiln 2 underwent substantial modifications, as described in previous reports, suggesting its possible use as a boiler. Below the imposing renaissance structures the excavations are bringing to light earlier evidence, as yet difficult to interpret, which however demonstrates that in the Monteleo area, in particular the plain that was to become the site of the alum mine, productive structures were already functioning. To date evidence is represented by stretches of wall made of roughly hewn stones, in some cases altered, bonded with earth. The walls are partially destroyed and completely covered by the profound restructuring of the plain following the construction of the alum kilns. The layers in phase with the walls produced a small amount of pottery, all datable to the 14th century, and significant fragments of copper and one lump of slag. Lastly, at a short distance from the walls a large mound of stones broken into homogeneous sized lumps was found; these were heavily altered but not yet subjected to firing, further proof of the productive nature of the structures being excavated.

In 2011 excavations continued on the plateau beside road S.P. 398, which had been investigated in 2010 (Area 3000) exposing walled and productive structures. The 2011 excavation extended the trenches in areas 3000, A, B, and D, and opened a new area (Area 3000 E). These areas were extended with the aim of gaining further understanding of the site’s diverse functions. Area A was extended to the south, in the space in front of the mouth of the circular casting structure already investigated in 2010 and whose function remains difficult to interpret. The removal of a substantial deposit formed by accumulations of inert materials, waste from productive activities and work surfaces, exposed part of the _praefurnium_ belonging to the casting structure. It also showed that the ground level in Area 3000 had been substantially raised in a relatively late phase between the second half of the 16th century and the first half of the 17th century. This rise in ground level, also documented in nearby areas, was created by dumping heavily siliceous (jaspers) inert materials, whose use was probably linked to their pozzolanic properties. The productive activities datable to this late period seemed to be attested by a patch of a surface made using these materials, perhaps linked to the crystallization phase of the product. There was a large amount of evidence for iron working. The slag was mainly attributable to forging activities. This was particularly well-documented in Area D, where evidence of all stages of this process were preserved. The actual forging was undertaken in small isolated structures and in forges installed “in batteries”; as well as the hole for housing the anvil support the excavation identified the places where the iron objects were piled up before being reintroduced into the production cycle. These comprised small iron bars and objects such as nails, punches, rings, fibulae, pegs and keys. This was a forger’s workshop, whose activity may either have related to the needs of the alum mine or been independent, that partially exploited pre-existing structures. The drastic transformation of the plateau, which occurred between the Renaissance period, the dating for the earliest evidence on area 3000, and the latest investments of the mid 18th century, was also documented in trench E. This trench, situated beside the modern road, revealed the presence of an _opus signinum_ surface (mentioned above) overlying a basalt paving. The preliminary interpretation of this space is that it was an area linked to the phases of alum crystallization. It was installed next to a pre-existing channel, which overlay a razed structure, of which only one corner was identified and is thought to date to the earliest phase attested so far on the site.

In September-October 2012, investigations continued in the area in front of the group of limekilns situated west of the Risecco torrent (Area 1000). Excavations had been carried out in this area in 2008-2010, at the same time as the investigation of the furnaces (Area 2000). This year’s excavations substantially enlarged the area under examination, extending it to the north (Trench 1) and south (Trench 3), by 40.30 (E-W) x 5 (N-S) m overall. _TRENCH 1_ Trench 1, at the far NE end of the excavation area, was dug in order to widen the investigation of the working area relating to furnace 1, in correspondence with the earlier structures found during the 2010 campaign. However, the layers excavated to date relate to a phase that is later than the 16th century phase of activity, and even the last layers, still in place, overlay these phases. Below the late phase of dumped quarry material the stratigraphy relating to the furnace use emerged, attested by the nature of the layers and their components, that is baked stones, fragments of burnt and vitrified brick/tile, and layers of charcoal and ash. _TRENCH 2_ Trench 2, covering an area of circa 60 m2 in front of furnaces 2 and 3, was in a zone that had been investigated in 2010. Important evidence was found here relating to a phase of use in this area that was otherwise undocumented. In fact, the foundations of the _praefurnium_ of furnace 3 cut the remains of a small casting structure. This was made up of a circular chamber built of two concentric structures of tiles placed on their edges forming an interspace, and by a small _praefurnium_ of flaring shape. The pottery recovered from the collapse and obliteration layers of the small structure indicate that it was abandoned and destroyed between the 14th and first half of the 15th centuries. To date it represents the only evidence of activities pre-dating that of the full 15th century, but later than the 14th century horizon already identified in 2010. _TRENCH 3_ Trench 3, at the southern end of area 1000, represented a substantial extension to the investigation of this zone. The most significant data from this season’s investigations was the identification, although partial, of a large structure built of perishable materials, in use at the same time as the 15th-16th century furnaces. It was attested by numerous postholes defining a perimeter inside which were heavily altered layers, bright red in colour, alternating with beaten surfaces with a large organic component. The structure was built at the edge of the plateau, which constituted the working area of the furnaces; the natural slope had been eliminated by the creation of a loose foundation, parts of which were visible below the postholes.

The 2013 excavations continued in three distinct areas defined in 2012, all situated in the area up against the battery of limekilns to the west of the Risecco torrent (Area 1000): Trench 1 (at the north end of area 1000), Trench 2 (in front of furnaces 2 and 3), and Trench 3 (at the south end of area 1000). TRENCH 1 An area 10 x 8.5 m was excavated. The upper part of the stratigraphy, relating to the use of the nearby Renaissance limekiln (F1), was removed revealing a series of levelling layers with a sandy matrix that marked a clear break in the activities of the 16th century and earlier kilns. These layers covered a substantial level of large irregular stones, probably a drainage feature that extended across the entire excavation area. The presence of walls dateable to a late medieval phase was indicated by the discovery of a large robber trench probably relating to activities on the late 15th century construction site, and the identification of large accumulations of brick/tile fragments, soil, and mortar. TRENCH 2 This trench covered an area of 22 x 7 m, between kilns 2 and 3. This season’s result provided better definition of the phases of use for the Renaissance furnaces and their construction phases. No less important was the excavation of a small productive structure situated inside the _praefurnium_ of furnace 3. The latter (excavation to be completed) comprised a circular chamber about 3 m in diameter built of brick and a splayed _praefurnium_ preserved for a length of 1.5 m. The find of numerous small copper fragments and a small tapping slag suggests that it was used in copper working. The furnace can be dated to within the first half of the 15th century, based on the materials found in the destruction and obliteration layers. TRENCH 3 The extension of Trench 3 to an area of about 10 m2 made it possible to further the investigation of a structure built in perishable material, already intercepted and described during the 2012 excavations. The 2013 campaign identified and removed a significant series of floors relating to this structure, made up of extremely compact layers containing abundant charcoal and whitish stones. Below were a series of stratigraphic contexts that had been created in order to extend the area of the plateau, and therefore of the hut itself. The hut’s long period of use was attested by the identification of another series of floors; among the finds were iron and copper fragments and some pottery sherds attributable to a late Etruscan horizon. The stratigraphy and the pottery show that the hut was used for various purposes and for various periods of time over several centuries. Indeed, it was possible to identify use in the Renaissance and a brief period of use in the medieval period (attested by fragments of zaffera relief and archaic majolica pottery both from beaten layers and from layers of dumped material). The presence of late Etruscan pottery, although found in secondary deposition, and the hut’s construction characteristics suggest that it was originally built in the Etruscan period, although this remains to be investigated further.

The 2014 excavations extended those of the previous year (Area 1000): Trench 1 (at the north end of area 1000), Trench 2 (in front of furnaces 2 and 3), and Trench 3 (at the south end of area 1000). The investigation identified a complex chronology, with occupation phases datable to the proto-historic period, possibly of a productive nature. TRENCH 1 In addition to investigating the stratigraphy relating to the earliest walls (remains of a late medieval furnace, 14th century), the excavations identified numerous other traces of metal casting activities, not linked to the first reduction of mixed sulphides, but to a different phase (liquation or another phase of possible extraction of an argentiferous mineral from copper), which further investigation may clarify. Production indicators included crucible fragments, stones, charcoal, bricks altered by exposure to fire and minute metallic fragments. In the same area, the remains of a possible forge were identified, also datable to a phase pre-dating the 15th century. Lastly, the analysis of the earliest walls identified a probable retaining wall, certainly pre-Roman, which can perhaps be associated with the fragments of early/mid Bronze Age pottery and lithic implements found in secondary deposition on the plateau (cf. Trench 3). TRENCH 2 Evidence of the construction site for the 15th century furnaces were identified, documented by the foundation cuts for the structures themselves and by substantial layers of more or less sterile material attesting the preparation of the area prior to their construction. The excavation also uncovered an earlier phase characterised by a different production use that was represented by the presence of a brick-built casting structure, linked to the exploitation of mixed sulphides. The structure, built during the first half of the 15th century, was formed by a circular chamber and a splayed _praefurnium_. A first analysis of the materials shows it was used as part of the copper producing process, but also showed a high content of silver in the metal found, which suggests that the silver was also extracted from the copper bearing minerals. TRENCH 3 The stratigraphy relating to the hut structure (see 2013) was removed. These layers produced several lithic tools made of arenite quartz, found in secondary deposition, interpreted as probable mallet heads, as well as flakes and small blocks with abraded surfaces. Along the external north-eastern edge of the hut, the excavation also identified a metalworking area (the layers contained brick fragments, copper, and two body sherds of slipped pottery). Below the removed contexts were the remains of the bottom of a small productive structure, preserved for about 80 cm in length, made up of calcinated stones, charcoal, and soil reddened by exposure to heat. Laboratory analyses should identify the mineral typology and process carried out in the structure.