Trajan's Forum (Hemicycle) and Via Biberatica (Trajan's Markets): An HHpXRF Study of the Provenance of Lava Paving in Ancient Rome (Italy)

This paper reports on geochemical data collected using a He-enabled Hand-Held portable XRF (HHpXRF) from lava paving stones in Trajan’s Forum Hemicycle and the Via Biberatica (Rome). Issues relating to HHpXRF field use and calibration are also addressed in detail. Using this instrument 355 analyses of the paving stones were collected and the data was processed using the standard techniques of igneous petrology and petrography. Provenancing was based on comparisons between the HHpXRF data and geological data from the abundant literature on Roman volcanic rocks. These comparisons placed the provenance of the paving stones in the Colli Albani, southeast of Rome. Further analysis using Zr/Y vs Nb/Y discriminant diagrams suggests that the paving stones were quarried from two sources both of which are represented in Trajan’s Forum and the Via Biberatica. The diagrams suggest that the sources lie within the Faete and Vallerano lava complexes. The latter were probably transported to the construction site by barge on the River Tiber and the former were easily accessible by carts along the Via Appia. The study establishes the potential of HHpXRF equipment for non-destructive analysis of paving stones both in Rome and at other sites in central Italy and challenges a number of assumptions about the supply of building materials to Rome based on intuition alone

Cation Distribution in Natural Chromites from Oman

Two specimens or natural chromite from the Oman ophiolite were studied using Mossbauer Spectroscopy (MS), X-ray Diffraction (XRD). and Scanning Electron Microscopy (SEM). The diffraction patterns obtained at room temperature showed that the two specimens have a face-centered cubic spinal structure. Their Mossbauer spectra at 295 K. 160 K and 78 K have been fitted to three doublets. assigned to two Fe 2+ at the tetrahedral (A1+,A2) sites and one Fe1+ at the octahedral (B) site. The ferrous-ferric ratio obtained from the Mossbauer analysis together with the atomic concentration derived from the microprobe data are used to derive the chemical formulae for the two specimens. The data also supports also supports  a model of ordered caution distribution in the specimens examined