The Bargiolina, a Striking Historical Stone from Monte Bracco (Piedmont, NW Italy) and a Possible Source of Industrial Minerals

Alessandro Cavallo,Giovanna Antonella Dino

doi:10.3390/su11164293

Abstract

The Bargiolina quartzite from Monte Bracco (western Alps, northern Italy) represents one of the most important historical ornamental stones of the Piedmont region. Known and used since the prehistoric age as substituting material for chert, it was celebrated by Leonardo da Vinci, and exploited at least since the XIII century, peaking in the XX century. It was extensively used in the construction of basilicas and noble palaces by famous architects of Piedmontese Baroque, for internal and external stone cladding. There are four main commercial and chromatic varieties, and the main technical feature is the regular schistosity, to obtain very thin natural split slabs. The different varieties have a homogeneous mineralogical composition and microstructure: A fine and homeoblastic grain size, and a granular—lepidoblastic texture, with regularly spaced schistose domains. The main rock-forming minerals are quartz, phengite, small amounts of K-feldspar and traces of plagioclase and chlorite. The yield rate of quarries is about 20%, and the poor exploitation planning of the past led to only partly exploited quarry benches, with a very poor residual yield. The large amount of quartz-rich quarry waste and the presence of kaolin-rich gneisses suggests the potential for novel applications in the field of industrial minerals.

Highlights

Known and used since the prehistoric age as substituting material for chert, it was celebrated by Leonardo da Vinci, and exploited at least since the XIII century, peaking in the XX century
Bargiolina is the term that defines a group of four main varieties of quartzites extracted from Monte Bracco (1306 m a.s.l.), an isolated mountain close to the village of Barge, approximately 40 km from Turin and Cuneo (Figure 1)
Known and used since the prehistoric age as substituting material for chert, the Bargiolina has been exploited in slabs at least since the XIII century, peaking in the XX century, used as internal and external facing because of its excellent technical proprieties [1,2]

Summary

Introduction

Bargiolina is the term that defines a group of four main varieties of quartzites extracted from Monte Bracco (1306 m a.s.l.), an isolated mountain close to the village of Barge (western Alps, northern Italy), approximately 40 km from Turin and Cuneo (Figure 1). The DMM is considered a slab of paleo-European continental crust, involved in Alpine-related E-dipping subduction, W-verging continental collision and deep crust/mantle indentation [10,11], and is stacked in the axial sector of the Western Alps and tectonically overlain by blueschist-facies and eclogite-facies meta-ophiolite units. Ortho- and paragneiss-hosted lenses and seams of quartzites (the alpine metamorphic product of the quartz-arenitic Permo-Triassic cover), are cropping out only towards the uppermost part of Monte Bracco (between 1100 and 1300 m a.s.l., an area of approximately 1.5 km2) and have been quarried as ornamental stones (Bargiolina). Due to the abundance and good quality of kaolin, extensive extraction occurred in the past (up to 50 kt/y till 1997)

Exploitation Setting

Discussion and Perspectives

Findings

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