Figure 13 - Monteverde tuff used at the theatre

The Kinds of Tuff used in Ostian construction

Geoarchaeological Aspects
Author:
Gioacchino Lena
Tuff (also known as volcanic tufa)[1] was among the first building materials employed at Ostia. The earliest examples of this rock were not of the highest quality, and were probably chosen for their ease of quarrying and transport. Over time, builders utilized tuff of increasingly better quality, and eventually even color may have become a factor in choosing the right tuff for a building project.

Tuff was used consistently until the second century CE at which point it dwindled in popularity until it disappeared almost completely, only to reappear with some frequency in the third and fourth centuries CE and beyond. This reappearance may have been due to the reuse of discarded materials, or perhaps resulted from the reopening of tuff quarries. [2] A close examination of the types of tuff extant in the buildings of Ostia has revealed that here, unlike at Rome, there was not such a wide variety of tuff; in fact only four to seven types are represented at the seaside colony. Nevertheless, tuff was used in similar ways at Rome and Ostia, and always depended on the opening of new quarries around the city, the improvement of quarrying techniques, and the technical characteristics of the materials themselves (Figure 1).

For full screen visualisation of the plan in a new window click on the image

Figure 1 – Plan of the overall distribution of the individual tuffs of Ostia

Figure 1 – Plan of the overall distribution of the individual tuffs of Ostia

a) Granular tuff AKA pisolithic tuff AKA cappellaccio
The granular tuff, or pisolithic tuff (so called due to the abundance of pisolites in the rock’s matrix) or even cappellaccio[3] is a tuff of light grey color when dry, grey-brown when wet. It is characterized by whitish leucite crystals throughout. At Ostia construction in granular tuff belonging to the first period of the castrum have been reported in the foundations of the earliest buildings and should also constitute the foundations in opus quadratum of the walls of the fourth-century fortification. The walls sit upon a light foundation consisting of a double course of granular tuff blocks, about 55 cm. high.[4]

Unfortunately the excavations carried out all over Ostia in anticipation of the Universal Exposition of 1942 (which, due to the war, never took place) have covered up all traces of this material and nothing can be seen from the present ground level.

b) Yellow tuff from Via Tiberina, and/or the straw-yellow tuff of Grotta Oscura
The yellow tuff (tufo giallo) of Via Tiberina is similar to that which is found to the north of Rome at Grotta Oscura. In the region around Rome this tuff came into use  after the granular tuff, perhaps as a result of an improvement in technical knowledge on the part of Roman quarrymen.[5] This tuff has uniform yellowish color, is quite porous, of medium firmness and has better technical characteristics than the pisolithic tuff. Depending on its specific composition, after prolonged contact with air the casting veins and inclusions cause this tuff to crumble easily. Despite these deficiencies in physical and technical characteristics, yellow tuff was widely used as a building material in Rome from about the fourth century BCE until the Augustan period. This was mainly due to the ease with which it could be extracted and transported to the city. In fact, the quarries stood close to the Tiber River, which provided safe and economical transport. This tuff went out of use after the Augustan period.[6]

According to De Angelis d’Ossat,[7] this tuff (like the so-called cappellaccio) appeared in several opus incertum constructions along with the yellow pisolithic tuff and the ubiquitous Monteverde tuff. Current research has been unable to verify its existence.

c) Yellow lithoid tuff from “Prima Porta”
The most visible outcrop of this tuff, on top of the yellow (giallastro) tuff, is found in the area of the “Prima Porta” (Via Flaminia) and is indicated by an inscription which commemorates the battle of Constantine against Maxentius; on top of this one sits the Fidenae tuff.[8] It is the hardest of the yellow tuff, but it is less compact due to the minute cavities left by decomposed plant matter; fossils are often found in these cavities. The color tends to pale yellow, with numerous yellow pumice inclusions. De Angelis d’Ossat reported the presence of this tuff in some structures.[9] Currently there are no visible examples with the possible exception of a series of small tuff blocks used in the face of a few buildings, alternating with Monteverde tuff.

d) Fidenae tuff with black pumice
This tuff is semilithoid in nature and more compact than the cappellaccio. The uniqueness and the recognizability of this tuff consist in the abundance of pumice and black lava slags which erupted from the volcano and mixed with an ashy, reddish mass.[10] To the naked eye it appears to have a coarse texture, it is grainy with the poor technical characteristics; the lava inclusions can also be very large with sharp edges (Figures 2 & 3).

Figure 2 – A wall of the castrum in Fidenae tuff

Figure 2 – A wall of the castrum in Fidenae tuff

Figure 3 - Fidenae tuff under a microscope (2,5x NP)

Figure 3 – Fidenae tuff under a microscope (2,5x NP)

In antiquity, the majority of this tuff was mined from the Castel Giubileo quarries. These quarries are long gone. The outcrop rests upon an older deposit of yellow lithoid tuff and is covered by another thin layer of friable yellow-grey tuff, which is more recent.[11] At Ostia this tuff is used in the two adjacent rows of opus quadratum blocks with the foundations of the castrum circuit, as well as its gates.

e) Yellowish pisolithic tuff “Due Case”
One variety of yellowish pisolithic tuff is known as “Due Case” (Two Houses), it comes from a place of the same name along the Via Flaminia.[12] Yellowish or light yellow, coarse-grained, very friable, this tuff also contains apowdery pumice that is even more yellow, but occasionally tend toward grey (Figure 4).

Figure 4 – Wall of the castrum and wall of the shops in Fidenae tuff and yellow pisolithic tuff “Due Case”

Figure 4 – Wall of the castrum and wall of the shops in Fidenae tuff and yellow pisolithic tuff “Due Case”

Close inspection reveals inclusions consisting of fragments of red tuff and sedimentary rocks (Figures 5 & 6).

Figure 5 – Parallelepiped blocks from the commercial structure on the Via del Mitrei dei Serpenti, in yellow pisolithic tuff “Due Case”

Figure 5 – Parallelepiped blocks from the commercial structure on the Via del Mitrei dei Serpenti, in yellow pisolithic tuff “Due Case”

Figure 6 – Yellow pisolithic tuff “Due Case” under a microscope (crossed nicols) (2,5 x NX)

Figure 6 – Yellow pisolithic tuff “Due Case” under a microscope (crossed nicols) (2,5 x NX)

The technical characteristics are poor. Many of the yellowish pisolithic blocks at Ostia have fractures extending from top to bottom which have come about due to the rock’s poor resistance to the compression exerted by the weight of the superstructure. On some blocks you will also notice a hint of layering due to different explosive episodes. The places where this tuff can be found today are indicated in Figure 7.

For full screen visualisation of the plan in a new window click on the image

Figure 7 – General distribution of yellow pisolithic tuff at Ostia

Figure 7 – General distribution of yellow pisolithic tuff at Ostia

a) Aniene tuff
Around the middle of the second century BCE, Roman builders had begun to recognize the inadequacies of the building stones of previous centuries. Thus they opened a new series of quarries along the Aniene river. The riverside location ensured a smooth transportation from Rome to Ostia.[13] The best-known quarries were located on the two riverbanks at Salone and Tor Cervara, but the Aniene tuff was generally quarried from the lower course of the river.[14] Aniene tuff is a lithoid tuff, consistent with the Monteverde tuff, from which it is often difficult—if not impossible—to distinguish. The ancients dubbed it lapis ruber (red stone). It has a reddish and variable grain, from coarse to very fine, depending on the point of the riverbank from which it was extracted. As noted before, it is a hard material and it is resistant to weathering (Figures 8 & 9 ). It was thought to impervious to fire: for this reason Nero had it used in the reconstruction of the lower floors of houses after the great fire of 64 CE.

Figure 8 – Tuff blocks on the temple of Roma and Augustus in Aniene

Figure 8 – Tuff blocks on the temple of Roma and Augustus in Aniene

Figure 9 – Aniene tuff under a microscope (parallel nicols) (2,5 x NP)

Figure 9 – Aniene tuff under a microscope (parallel nicols) (2,5 x NP)

The places where this tuff can be found today are indicated in Figure 10 .

For full screen visualisation of the plan in a new window click on the image

Figure 10 – General distribution of Aniene tuff at Ostia

Figure 10 – General distribution of Aniene tuff at Ostia

g) Monteverde tuff AKA tuff lionato
We do not know the ancient name of this stone; the name we attribute to it today actually specifies the location where the main quarry is found, at the foot of the Janiculum between the old Trastevere station and Magliana.[15]

Tenney Frank was the first to distinguish four different stages of Monteverde tuff deposits: of these the Romans only used two.[16] One is no longer preserved anywhere due to the flooding of the Tiber, while the other, which is the hardest and is found at the lowest depth, was mined and used in more recent times. It is red-brown in color, occasionally tending toward yellow or orange, the grain is variable, from medium to very fine and compact (Figures 11, 12, 13 & 14).

Figure 11 - Monteverde tuff in the Grandi Horrea

Figure 11 – Monteverde tuff in the Grandi Horrea

Figure 12 - Monteverde tuff under a microscope (parallel nicols) (2.5 x NP)

Figure 12 – Monteverde tuff under a microscope (parallel nicols) (2.5 x NP)

Figure 13 - Monteverde tuff used at the theatre

Figure 13 – Monteverde tuff used at the theatre

Figure 14 - Monteverde tuff under a microscope (crossed nicols) (2,5 x NX)

Figure 14 – Monteverde tuff under a microscope (crossed nicols) (2,5 x NX)

Since this tuff shows the same essential characteristics but displays wide variances in color, texture and proportions of inclusions, we must conclude that the differences are attributed to the fact that they came from different quarries or from different parts of the same quarry.

The monuments in which Monteverde tuff has been used are shown in Figure 15.

For full screen visualisation of the plan in a new window click on the image

Figure 15 – General distribution of Monteverde tuff

Figure 15 – General distribution of Monteverde tuff

Concluding remarks
As we have seen in this survey, only four of the seven types of tuff documented prior to the 1960’s can be seen at Ostia today. The Cappellaccio, the yellow tuff of Prima Porta and the Grotta Oscura, all of which were identified by De Angelis D’Ossat, are no longer visible.[17] In most cases, De Angelis D’Ossat did not specify the buildings in which they were employed. He stated only that they were used in buildings belonging to the ear of the foundation of the castrum (Cappellaccio), in walls of coarse opus incertum (Prima Porta) and opus incertum (Grotta Oscura). Some walls have not retained their original appearance due to restorations and renovations, and therefore it has not been possible to reexamine De Angelis D’Ossat’s claims. The rock types which can still be seen today are: Fidenae tuff, the yellowish pisolithic tuff, the Aniene tuff, and tuff Monteverde. (Figures 1, 7, 10, 15). The first is only present in the walls of the castrum (and in some shapeless blocks in the Porta Romana necropolis) so we can deduce that its use was limited only to the period of Ostia’s foundation.

The use of yellowish pisolithic tuff seems to have endured for a long time. In fact, it seems to have been employed from as early as the third century BCE (walls in the Piazzetta dei Lari and Via del Larario and shops huddled by the walls of the castrum)[18] to the second century CE (the commercial building adjacent to Mithraeum of the Serpents, dating to the Hadrianic period)[19] and, in one case, even at the beginning of the third century CE (the commercial structure on the Via del Mitreo dei Serpenti, which dates to the beginning of the Severan period).[20] In the case of these later uses, we might conclude that tuff was being recycled from older buildings or perhaps that the old quarries were reopened.

The two other types of tuff, Aniene and Monteverde, share similar characteristics and are spread throughout Ostia. The former (Figure 10) is less commonly employed, while the latter (Figure 15 ) predominates in many structures. This wide use of Monteverde at Ostia is not reflected in Rome, where the material seems to have been less popular. Monteverde is found as early as the second century BCE and its use continued into the second century CE (Palazzo Imperiale, Caseggiato dei Triclini). Monteverde tuff was probably also used in the later building phases, for reconstructions and renovations of various kinds, but it can be difficult to distinguish between original use and reuse. It is no longer found with the same frequency after the third century CE, and where it is found it is probably reused material. They type employed at Ostia, which is easily recognizable to the naked eye, presents a considerable variety in respect to color (more or less reddish), composition (coarse to very fine) and inclusions (pumice, etc.). These differences can be ascribed to the different layers of the quarry from which the tuff was extracted.

In conclusion, of the many varieties of tuff employed in Rome, only a few are used in Ostia. The most predominant of these was the Monteverde tuff.

Translated by Mary Jane Cuyler

Works Cited

  • Bianchi 1998: E. Bianchi, “Il Caseggiato del Sole e gli edifici attigui”, in Bollettino di Archeologia49-50, 1998, pp. 115-130.
  • Blake 1947: M.E. Blake, Roman construction in Italy from the prehistoric period to Augustus, Washington, 1947.
  • Calza et al. 1953: G Calza, G. Becatti, I. Gismondi, G. De Angelis d’Ossat, H. Bloch,Scavi di Ostia I. Topografia generale, Roma, 1953.
  • De Rita, Giampaolo 1999: D. De Rita, C. Giampaolo, “Monuments as “Geotopes”: volcanic building stones from the roman area used to construct ancient,” in Memorie Descrittive della Carta Geologica d’ItaliaLIV, 1999, pp. 207-218.
  • Frank, 1924: T. Frank, Roman buildings of the Republic, Roma, 1924.
  • Lugli 1957: G. Lugli, La tecnica edilizia romana con particolare riferimento a Roma e il Lazio, Roma, 1957.
  • Penta 1955: F. Penta, “I Materiali da costruzione del Lazio”, in La Ricerca Scientifica,26, Roma, 1955.


[1] Translator’s note: The Italian tufo refers to a volcanic rock. The official geological term for this material in English is “tuff” but it is very commonly referred to as “tufa” by native English-speaking archaeologists. It is best to avoid the term “tufa” because it can be confused with limestone or calcareous tufa, which is not volcanic.
[2] Calza et al. 1953
[3] The name derives from the fact that this type of rock alternates in layers with pozzolana within the quarries, and therefore the men quarrying the pozzolana were required to demolish the tuff that sat like a hat (“cappello”) on the layer they wished to extract (Lugli 1957, p. 171).
[4] Calza et al. 1953, pp.181-193; De Rita, Giampaolo 1999, pp. 212-213
[5] De Rita, Giampaolo 1999, p. 212
[6] De Rita e Giampaolo 1999, p. 213
[7] Calza et al., 1953, p. 186
[8] The stratigraphic sequence from bottom to top: = 1) yellow pisolithic tuff (tufo giallastro pisolitico); 2 )yellow lithoid tuff (tufo giallo litoide); 3) Fidenae tuff
[9] Calza et al 1953, p.184.
[10] Frank 1924, p. 17; Blake 1947, pp. 26-27; Calza et al. 1953, pp. 209-210; Penta 1956, p. 124; Lugli 1957, pp. 253-257
[11] Frank 1924, pp.17, 20; Blake 1947, pp. 26-27; Lugli 1957, pp. 255-257
[12] Calza et al 1953, p. 209
[13] Frank 1924, p. 26; Lugli 1957, p. 185
[14] Frank 1924, p. 27; Blake 1947, pp. 29-30; Penta 1956, pp.118-122; Lugli 1957, p. 309
[15] Blake 1947, p. 29; Penta 1956, p.118; Lugli 1957, p. 311
[16] Frank 1924, p. 31
[17] Calza et al. 1953, 181-210
[18] Calza et  al. 1953, p.182
[19] Bianchi 1998, pp. 115, 128
[20] Bianchi 1998, pp. 115, 129

This text has been published under a Creative Commons License CC BY-NC-SA 4.0. Feel free to publish it on your websites, blogs… under the following conditions: You must give appropriate credit, mention the author and provide a link to this original publication and to the license indicated above. You may not use the material for commercial purposes.