Basalt used to be called pietra di ferro by the ancients, since it was confused with very finely grained granite that merited such a name. It is however a volcanic product that generally is presented in the form of columns and pilasters. It is of a compact texture, tough, and very hard, in which no foreign substance is found. It can barely be worked, and takes a polish with difficulty.
§ I Ancient basalts (Basalti antiche)
671. (160.1) Pietra di paragone. Marmor Lydium. Authorities agree that Lydian stone (pietra lidia) corresponds to touchstone. Indeed Pliny 95 says that the Lydian stone is a type of basalt used for testing gold. In colour it is consistently black; it used to be found in Lydia, a province of Asia Minor. There is a beautiful urn of this stone under the High Altar of the Church of S. Croce in Gerusalemme. (Very rare).
672. (160.2) Basalte scura. Marmor Aethiopicum. Although another black basalt similar to the above might have been be found in Ethiopia, nonetheless rarer and more beautiful than all was this dark one, very similar to the colour of coffee. The only known example of this stone is one small Bacchus lying in the Galleria de' Candelabri of the Vatican Museum no.1385,[p161] and which can be seen restored with green basalt, which demonstrates that such stone would be (rare).
673. (161.3) Basalte verde. This stone is absolutely monochrome, and of a dark apple green. In the octagonal courtyard of the Vatican Museum there is of this stone a large and beautiful water container, or it might be a bath. (Very rare).
674. (161.4) Basalte listata. This basalt is composed of the two above basalts inasmuch as the ground is green, and the stripes are the colour of coffee. (Very rare).
675. (161.5) Basalte fiorita. It has a green ground covered all over with small whitish spots. (Very rare).
§ II Italian basalts (Basalti d'Italia)
676. (161.1) Basalte di Venezia. Very deep apple green all over, with some scarcely visible black spots. (Rare).
677. (161.2) Another of a little lighter green, with white and faded yellow veins. (Less rare).