The Settignano quarries yielded macigno, a fine-grained grey sandstone that was much prized in Florence. It is a gravely beautiful material in a range of dark-greenish and bluish greys, fine enough to carve in crisp detail and with a quality of simultaneously absorbing and reflecting the light, producing a paradoxical impression of dark luminosity.
This is the material that Brunelleschi used for the columns and capitals of his buildings. Michelangelo would employ it in the same way in his projects at San Lorenzo in Florence.
The Florentines, being interested in this stone enough to make fine distinctions, gave names to the differing grades, the finest type being pietra del fossato, and the others including pietra serena and pietra forte.
Michelangelo, who had immense sensitivity to stone, went further than these broad categories. He knew that each quarry, every stratum, would produce material of subtly differing character. The contract for the stairs and two doors of the library Michelangelo was building at San Lorenzo in the 1520s stipulated that the pietra serena supplied should be of the same ‘colour and flavour’ (‘ colore et sapore’) as in the sample. ‘Flavour’ is a wonderful word to use of stone: bringing out its sensuous character as if it were actually edible.
When he designed buildings in Rome, Michelangelo was attentive to the qualities of the local material, travertine, a limestone noted for the pits and troughs in its surface – as different in its flavour and colour from Florentine sandstone as roast beef is from pâté de foie gras. His use of travertine for the walls of St Peter’s and the palaces on the Capitoline Hill made the most of its rugged nature.
For sculpture he used only the finest type of pure white marble, known as statuario, found particularly in certain quarries above Carrara. Even this sculptor’s marble, according to the sculptor and goldsmith Benvenuto Cellini, came in at least five or six grades, the first having a ‘very coarse grain’ and the softest, which he describes almost like flesh, ‘the most cohesive, the most beautiful and the tenderest marble in the world to work from’.
Michelangelo was renowned for his ability to discern the quality of a potential piece while it was still in the rockface. When he was engaged from 1516 onwards on large construction projects at San Lorenzo in Florence which involved the quarrying, transport, dressing and carving of huge amounts of both marble and macigno, a majority of the masons he employed were from Settignano.
Gayford, Martin. Michelangelo: His Epic Life (Kindle Locations 803-811). Penguin Books Ltd. Kindle Edition.