§ 6 Of Granite
There is another sort of extremely hard stone, much coarser and speckled with black and white and sometimes with red, which, on account of its grain and consistency, is commonly called granite.41 In Egypt it exists in solid masses of immense size that can be quarried in pieces incredibly long, such as are seen now-a-days in Rome in obelisks, needles, pyramids, columns, and in those enormous vessels for baths which we have at San Pietro in Vincola, at San Salvadore del Lauro and at San Marco.42 It is also seen in columns without number, which for hardness and compactness have had nothing to fear from fire or sword, so that time itself, that drives everything to ruin, not only has not destroyed them but has not even altered their colour. It was for this reason that the Egyptians made use of granite in the service of their dead, writing on these obelisks in their strange characters the lives of the great, to preserve the memory of their prowess and nobility.
From Egypt there used also to come another variety of grey granite, where the black and white specks draw rather towards green. It is certainly very hard, not so hard however, but that our stonecutters, in the building of St. Peter’s, have made use of the fragments they have found, in such a manner that by means of the temper of the tools at present adopted, they have reduced the columns and other pieces to the desired slenderness and have given them a polish equal to that of porphyry.
Many parts of Italy are enriched with this grey granite, but the largest blocks found are in the island of Elba, where the Romans kept men continually employed in quarrying countless pieces of this rock.43 Some of the columns of the portico of the Ritonda are made of it, and they are very beautiful and of extraordinary size.44 It is noticed that the stone when in the quarry is far softer and more easy to work than after it has lain exposed.45 It is true that for the most part it must be worked with picks that have a point, like those used for porphyry, and at the other end a sharp edge like a toothed chisel.46 From a piece of this granite which was detached from the mass, Duke Cosimo has hollowed out a round basin twelve braccia broad in every direction and a table of the same length for the palace and garden of the Pitti.47