§ 17 Of Pietra Forte102
The pietra forte is quarried in many places; it resists rain, sun, frost, and every trial, and demands time to work it, but it behaves very well; it does not exist in very large blocks.103 Both by the Goths104 and by the moderns have been constructed of this stone the most beautiful buildings to be found in Tuscany, as can be seen in Florence in the filling of the two arches, which form the principal doors of the oratory of Orsanmichele,105 for these are truly admirable things and worked with the utmost care. Of this same stone there are throughout the city, as has been said, many statues and coats of arms,106 as for instance in the Fortress and various other places. It is yellowish in colour with fine white veins that add greatly to its attractiveness, and it is sometimes employed for statues where there are to be fountains, because it is not injured by water. The walls of the palace of the Signori, the Loggia, and Orsanmichele are built of it, also the whole interior of the fabric of Santa Maria del Fiore, as well as all the bridges of our city, the Palace of the Pitti and that of the Strozzi families. It has to be worked with picks because it is very compact. Similarly, the other stones mentioned above must be treated in the manner already explained for the working of marble and other sorts of stones.