Geochemical Characterization of Archaeological Lime Mortars: Provenance Inputs*

Abstract

Chemical and mineralogical analyses were carried out on historical lime mortars from the parish church of Santa María La Real (Guipúzcoa). The study included various periods ranging from Roman to modern times and allowed the identification of various types of raw materials. In order to obtain pure binder, free of carbonate aggregates and charcoal particles, an innovative binder separation method was implemented. The chemical composition of the binder allows discrimination of different provenance areas for the raw materials, although those areas do not correlate with specific historical periods. In addition, the influence of burial processes on the primeval chemical features has been assessed and reveals that modern mortars display greater chemical modification than the Roman mortars.

Comparisons of ancient mortars and hydraulic cements through in situ analyses by portable X‐ray fluorescence spectrometry

“…Zn has been reported previously in ancient mortars [12,18,19] but only at a trace level. The elevated Zn could be the result of sphalerite (ZnS) or smithsonite (ZnCO 3 ) in the material.…”

“…Zn and Rb have been previously reported at trace levels in ancient mortars and are most likely in detritic minerals used as aggregates in the mortar. [12,19,22] The Pb may be present from water used in the hydraulic cement preparation; a water system utilizing lead pipes was found partially intact at the site.…”

“…Similar trace metal profiles were observed for mortars within the same site, however, thus demonstrating elemental homogeneity in some mortars. [12,18,19] Also, trace elements in mortars from differing historical periods have been reported as they relate to identification of provenance of the raw materials. [19] Use of a portable and nondestructive instrument such as an XRF spectrometer could provide both major and minor elemental composition information while leaving the excavation site intact.…”

“…[12,18,19] Also, trace elements in mortars from differing historical periods have been reported as they relate to identification of provenance of the raw materials. [19] Use of a portable and nondestructive instrument such as an XRF spectrometer could provide both major and minor elemental composition information while leaving the excavation site intact. The short analysis times with this instrument also permit measurements on many samples, thus providing the statistical degrees of freedom necessary for valid comparisons among mortars.…”

Indirect chronology method employing rare earth elements to identify Sagunto Castle mortar construction periods

“…Innovative methodological approaches employing REE have been recently established to tackle challenging archaeological problems related to the polished stone raw material origins [23] and soil formations [24,25]. REE and other trace elements analysis have been used by some authors to identify mortar raw materials [2,3,26,27,28]. For example, studies of REE in mortar samples were carried out by Mirello et al [27] employing La/Ce ratio, to identify the provenance of limestone employed to made the mortars at the Aztec Sacred Precinct of Tenochtitlan (Mexico City).…”