Archaeometry 47, 3 (2005) 485– 510. Printed in Singapore * Received 12 May 2004; accepted 12 December 2004. † Address for correspondence: 17635 Juday Lake Drive, South Bend, Indiana 46635, USA. © University of Oxford, 2005 Blackwell Publishing, Ltd. Oxford, UK ARCH Archaeometry 0003-813X © University of Oxford, 2005 February 2005 47 3 Original Article Tuff and travertine building stone in ancient Rome M. D. Jackson et al. THE JUDICIOUS SELECTION AND PRESERVATION OF TUFF AND TRAVERTINE BUILDING STONE IN ANCIENT ROME * M. D. JACKSON Department of History, P.O. Box 6023, Northern Arizona University, Flagstaff, Arizona 86011, USA F. MARRA Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, Rome 00143, Italy R. L. HAY Geosciences Department, University of Arizona, Tucson, Arizona 85721, USA C. CAWOOD 3981 N. Luzern Circle, Flagstaff, Arizona 86004, USA and E. M. WINKLER† Department of Civil Engineering and Geological Sciences, University of Notre Dame, South Bend, Indiana 46635, USA The Republican and early Imperial monuments of Rome are, for the most part, built of tuffs quarried from at least seven pyroclastic deposits erupted from nearby Monti Sabatini and Alban Hills volcanoes. Remarks by Vitruvius (2.7.1–5), field observations of the monuments, and petrographic and rock testing studies of samples from Roman quarries demonstrate that Roman builders developed a good knowledge of the diverse material properties of the tuffs over centuries of use and exposure. Measurements of compressive strength, specific gravity, water absorption and adsorption of water vapour confirm that the petrographic characteristics of each tuff lithology strongly influence its strength and durability. Early construction utilized weakly durable, soft or vitric tuffs such as Tufo del Palatino or Tufo Giallo della Via Tiberina that are susceptible to decay, as at Temple C (290 BC) of the Largo Argentina Sacred Area. Late Republican structures, such as the Temple of Portunus (80–90 BC), employed somewhat durable, vitric–lithic Tufo Lionato reinforced with travertine, a durable limestone quarried near Tivoli. Roman builders selected the material properties of the tuffs to advantage for specific structural elements within large public monuments of the first century BC and the first century AD, as at the tabernae of the Forum of Caesar (46 BC), where an upper storey of lightweight Tufo Lionato is supported by robust, lithic– crystal Lapis Gabinus pillars and flat arches reinforced with travertine. The tuffs are not very durable building stones; Romans preserved them with protective stucco, and travertine and marble cladding. Their high water intake, coupled with direct exposure to rain, daily fluctuations in relative humidity and urban weathering at present makes them especially vulnerable to decay. KEYWORDS: ANCIENT ROME, BUILDING STONES, TUFF, TRAVERTINE, PETROGRAPHIC CHARACTERISTICS, PHYSICAL PROPERTIES © University of Oxford, 2005