RESEARCH ARTICLE © ARQUEOLOGÍA IBEROAMERICANA 40 (2018): 81-92. ISSN 1989-4104. http://laiesken.net/arqueologia/. INVESTIGATIONS OF HELLENISTIC MORTAR FROM UMM QAIS (GADARA), JORDAN Firas Alawneh, 1 Eyad Almasri 2 1 Department of Conservation Science, Queen Rania Faculty of Tourism & Heritage, Hashemite University, Zarqa, Jordan; 2 Department of Sustainable Tourism, Queen Rania Faculty of Tourism & Heritage, Hashemite University, Zarqa, Jordan (Corresponding Author: firas-alawneh@hu.edu.jo) Received: October 3, 2018. Accepted: October 14, 2018. Published: December 21, 2018. Edited & Published by Pascual Izquierdo-Egea. Endorsed by Atef Shiyab & Maher Tarboush. English proofreading by Emily Lena Jones. Arqueol. Iberoam. Open Access Journal. License CC BY 3.0 ES. http://purl.org/aia/4009. Figure 1. Location map of the study area. ABSTRACT. Ancient mortars have been widely studied, in connection with both diagnosis and applications re- quired for restoration. This study is primarily based on analyses of different mortar samples from a Hellenistic temple. The study was done by means of a polarizing mi- croscope equipped for observations in transmitted and re- flected light; and X-ray powder diffraction (XRD). Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM-EDS) were also used to confirm and supplement the microscopic data, and wet chemical analyses were performed on the acid filtrate for soluble oxides of Fe, Al, Ca, Mg, S, Na and K. Chemical and petrographic analysis were used to determine chemical composition and physical properties, which in turn provide an in-depth understanding of the structural behavior and durability characteristics as they relate to the composition. The re- sults show that the plaster used was a lime-based mortar. The cementing binder was a lime (identified by spot test) with fossilized shell, very fine grain size quartz, and some other minerals as the aggregate. The EDS analysis showed the presence of calcium and a small proportion of magne- sium; in addition, silicon, aluminum, potassium, and iron were detected. Possibly, the silicate compounds contributed to the hydraulic component. We found strong similarities among mortar samples used in the temple. Physical meth- ods provided useful information on the mineralogical com- pounds and the surface structures of samples, allowing for the postulation of deterioration mechanisms and overall decay, including the identification and crystalline morphol- ogy of reaction products and salts. These results aid in both understanding the technology of historic mortars and plan- ning the restoration of these mortars. KEYWORDS. Mortar analysis; SEM-EDS; Gadara; Lime; Restoration. INTRODUCTION Degradation of building materials in monumental structures is a well-known phenomenon. In antiquity, people seemed to know, to distinguish, and to classify materials according to their durability and suitability. Morgan (1960) states, for instance, that some stones