Fig. 52 - Geometry of cubetti. Fig. 53 - Exterior paving using cubetti at the Piazza del Castello in Fornace - Trento, Italy. Cubetti: shape and geometry Porphyry cubetti are derived from unshaped slabs selected during the first sorting phase at the quarry. They are produced by compression-splitting using hydraulic presses. They are more or less cubed in shape, even though the faces are not perpendicular one to the other, especially when hand-made. The upper face of the cube is natural and rather even, providing a good traffic surface. The split sides although rough allow for close jointing (Fig. 52). Porphyry cubetti are produced in varying sizes, the most common on the market having side (A) ranging from 4 to 20 cm while height (C) may vary from 4 to 20 cm according to the proportions indicated in Table 7. Choice of one size instead of another depends on the intended use. Usually, 4/6 to 6/8 cubetti are used for pedestrian and/or light vehicle traffic surfaces, while 8/10 to 14/18 cubetti are used for heavy vehicle traffic surfaces (Fig. 53).

Table 7 - morphological characteristics and applications of "cubetti".