§ 16 Of Pietra Serena
There only remains now the pietra serena and the grey stone called ‘macigno’95 and the pietra forte which is much used in the mountainous parts of Italy, especially in Tuscany, and most of all in Florence and her territory. The stone that they call pietra serena96 draws towards blue or rather towards a greyish tint. There are quarries of it in many places near Arezzo, at Cortona, at Volterra, and throughout the Apennines. The finest is in the hills of Fiesole, and it is obtained there in blocks of very great size, as we see in all the edifices constructed in Florence by Filippo di Ser Brunellesco, who had all the stones needed for the churches of San Lorenzo and of Santo Spirito quarried there, and also an unlimited quantity which are in every building throughout the city. It is a very beautiful stone to look at, but it wastes away and exfoliates where it is subjected to damp, rain, or frost. Under cover however it will last for ever. Much more durable than this and of finer colour is a sort of bluish stone, in our day called ‘pietra del fossato.’97 When quarried, the first layer is gravelly and coarse, the second is never free from knots and fissures, the third is admirable being much finer in grain. Michelagnolo used this, because of its yielding grain, in building the Library and Sacristy of San Lorenzo for Pope Clement, and he has had the mouldings, columns, and every part of the work executed with such great care that even if it were of silver it would not look so well.98 The stone takes on a very fine polish, so much so that nothing better in this kind of material could be wished for. On this account it was forbidden by law that the stone be used in Florence for other than public buildings, unless permission had been obtained from the governing authorities.99 The Duke Cosimo has had a great quantity of this stone put into use, as for example, in the columns and ornaments of the loggia of the Mercato Nuovo, and for the work begun by Bandinello in the great audience chamber of the palace and also in the other hall which is opposite to it; but the greatest amount, more than ever used elsewhere, has been taken by his Excellency for the Strada de’ Magistrati,100 now in construction, after the design and under the direction of Giorgio Vasari of Arezzo. This stone demands as much time for working it as marble. It is so hard that water does not affect it and it withstands all other attacks of time.
Besides this there is another sort called pietra serena, found all over the hill, which is coarser, harder, and not so much coloured, and contains certain knots in the stone. It resists the influence of water and frost, and is useful for figures and carved ornaments. Of this is carved La Dovizia (Abundance), a figure from the hand of Donatello on the column of the Mercato Vecchio in Florence;101 and it serves also for many other statues executed by excellent sculptors, not only in this city, but throughout the territory.