The “Pietra Serena” stones of Brunelleschi's Cupola

Brunelleschi conceived the Santa Maria del Fiore (Florence Cathedral) Cupola as a self-sustaining structure. To that purpose, he introducd new techniques and a selected use of building materials. The archives of the Opera del Duomo show that particular materials were chosen for specific uses, and in many instances the precise quarry where the stones had to come from was specified. In the Brunelleschi's idea, the chains containing the outward thrusts of the Cupola involved a high structural relevance. These elements are made of a specific type of Pietra Serena, the ornamental stone derived from the excavation of the best-graded beds of Macigno sandstone. Brunelleschi selected some specific layers, outcropping at the “Trassinaia” quarry, peculiar for their mechanical strength. Though the Trassinaia quarry is frequently quoted in the Opera del Duomo documentation, its exact location remained uncertain so far. Detailed analysis of historical and recent cartography, together with landscape, geological and archeo-mining investigations, have now allowed to confidently identify this site in an ancient, abandoned quarry site settled on the right-side of a stream, unnamed at present but originally denominated “Trassinaia creek”. This discovery opens, therefore, new perspectives for comparative studies of compositional and mechanical characteristics of correlative stones on the Cupola and at quarry site.