Original paper
The stones of medieval buildings in Pisa and Lucca (western Tuscany, Italy). 3 - Green and white-pink quartzites from Mt. Pisano
Franzini, Marco; Lezzerini, Marco; Mannella, Lorenzo
European Journal of Mineralogy Volume 13 Number 1 (2001), p. 187 - 195
published: Jan 31, 2001
Abstract
In the framework of ongoing research on the building stones and mortars used throughout the Middle Ages in the cities of Pisa and Lucca (western Tuscany), the chemical, mineralogical, petrographical and main physical properties of 72 green and white-pink quartzite samples from Mt. Pisano (Tuscany, Italy) were determined. Data was collected on unweathered materials sampled from currently operating or inactive quarries. All the analysed samples can be described as belonging to a single compositional ''family'', whose members are mixtures, in different proportions, of silica and a ''residue'' with a nearly constant ratio amongst its chemical constituents. The white-pink quartzites have a quartz average content (71.60 %) somewhat higher than the green ones (64.93 %). The green and white-pink quartzites have very similar overall properties, and both are extremely resistant to degradation. They differ mostly in the average values of the bulk density (2.61 g/cm3 and 2.44 g/cm3 for green and white-pink quartzites, respectively), water imbibition coefficient (0.793 % and 1.617 % by weight), porosity (3.39 % and 9.40 % by volume) and grain size (175 μm and 344 μm). The white-pink quartzites were used much more often in construction than the green ones, probably owing to easier quarrying. The different applications and degrees of degradation of these quartzites are described with reference to historical monuments in Pisa and Lucca.