ROMAN BEDROCK MORTARS: NEW FINDINGS FOR INTERPRETING DATA AT THE ROMAN PINO DEL ORO GOLD MINES (SPAIN)

Abstract

The Pino del Oro gold mines, located in the northwestern Iberian Peninsula and more specifically in the Spanish province of Zamora, form part of the country‟s Roman Age mining heritage. These mines differ from all the others in the empire in one respect: they are characterised by the presence of quern-like depressions found in the nearby granitic outcrops where miners ground the ore. A series of petrological techniques was used to determine the most appropriate procedure for gathering information that would help clarify the significance of these man-made formations and whether the type of granite was a conditioning factor in the choice of grinding site. An analysis of the results yielded by the techniques deployed to characterise the two types of granite where the bedrock mortars are found showed that ultrasound velocity (Vp) and the hardness index are the two most suitable for futher research. On the grounds of the Vp and hardness fingings, a hypothesis is put forward on how to determine the stage of usability of the bedrock mortars.