Opera magazine
2026-03-02
The Paths of Stone: From the Heart of the Quarries to Piazza Duomo
Marbles, Rocks, and Clays: The Geography of Skin and Bone for the Cathedral, Baptistery, and Dome.
A sumptuous cladding of white, red and green marble entirely covers the Baptistery, the Bell Tower and the immense Cathedral of Florence: a unique masterpiece in terms of scale and refinement. The white-and-green geometric “garment” of the Baptistery was created in the 13th century; that of Giotto’s Bell Tower, where red also triumphs, dates to the 14th century; while the countless marble elements forming the skin of the Cathedral were installed from its foundation through the 16th century, except for the 19th-century façade, whose marble is marked by a fragility caused by the trauma of quarry extraction using explosives.
It is an enormous mosaic of hundreds of square meters of rather thick slabs, skillfully worked and installed by generations of master stoneworkers, who for centuries followed the designs of equally important artists. Yet this cosmos of stone does not end here: one must also take into account the marble floors inside — the 13th-century ones of the Baptistery and the 16th- and 17th-century ones of the Cathedral; nor can one forget the pietraforte used for walls and pillars, the clays for bricks and roof tiles, and finally the mortars that held the parts together. In order to secure access to these materials, the Opera del Duomo developed over the centuries a complex network of access to quarries, some in the immediate vicinity, others farther away and even in the territories of other States.
Let us now look at the principal stones among them.
The green marble, the so-called “serpentine of Prato”, takes its name from the quarry from which it was extracted, on Monte Ferrato, near the village of Figline, close to Prato, about 30 km from Florence (the quarry is now abandoned). It is a metamorphic rock, as beautiful in appearance as it is fragile: it “flakes,” as Vasari said. It became widespread in Tuscany, used in the typical bichrome decoration of Romanesque architecture and, because of its similarity to ancient green porphyry, in late Roman opus sectile inlays.
The “red” marble, on the other hand, was quarried from the 14th century onward in various locations: one type came from San Giusto a Monterantoli in Chianti, and another from Monsummano in the Val di Nievole, today in the province of Pistoia. A particular case concerns the red marble of the lower levels of the Bell Tower: a pink limestone with ammonites. Installed during the building campaign of Andrea Pisano, it seems that he went to his native land to seek out this lithotype, thus drawing from the quarries of the Counts Della Gherardesca near Avane (Pisa) and Sassetta (Livorno).
For white marble, the Opera could more easily draw from quarries it owned, first and foremost the renowned ones in the territory of Seravezza, Pietrasanta and Cappella, where the marble of brightness and purity for which it is still famous worldwide was extracted. From there came the block from which Michelangelo carved his David. Marble from Carrara, however, was difficult to transport and the route crossed non-Florentine territories. Another quarry was therefore used near the village of Campiglia (Livorno): this marble had been known since the time of the Roman Empire for its high quality.
More readily available was "pietraforte", the brownish sandstone used since ancient times for structural elements: the quarries were located within the city or in its immediate surroundings, at Maiano near Fiesole, in what later became the Boboli Gardens, at Monteripaldi between Pian dei Giullari and the Cascine del Riccio, at Monte Oliveto, at Le Campora and at Marignolle.
Closely related to "pietraforte" is another sandstone, "macigno", or "pietra serena", grey with a bluish hue, much weaker and therefore reserved for decorative elements. One quarry was located on the Fiesole side at Monte Ceceri, and another at Trassinaia, on the nearby hill of Settignano, owned by the Alessandri family on the hill of Vincigliata, between Settignano and Fiesole.
The clay for the tiles and bricks of the Dome was produced by the flooding of the Arno River and its tributaries, and it is no coincidence that Florence was famous for its kilns. Bricks for the Dome came from the kilns of the western countryside: Badia a Settimo, Lastra a Signa and Campi Bisenzio. The roof tiles covering both the Cathedral roofs and the sails of the Dome were supplied by the kilns of Impruneta, 10 kilometers from Florence (still today an internationally renowned excellence).
Finally, the mortar — the “cement” that held together this kaleidoscope of stone and clay — was made by mixing a limestone known as “alberese chiaro” (whose quarries were at Monte Morello and Pontassieve) with sand collected by the renaioli from the bed of the Arno.
When we admire our temples shining in the sun, even where there is no painted figure, mosaic or statue, we should not see only stone, nor mere ornament, but technical mastery, history and love of beauty, born of thousands of hands and radiating from the heart of a most fertile land: Tuscany
