Porphyry is a special extrusion rock. A complex of volcanic rocks extends over the region of Trentino-South Tyrol, known as the porphyritic platform of the river Adige/Etsch.
260 million years ago in the lower Permian an intensive volcanic activity started that lasted for more than many millions of years with alternating phases of eruptions and calmness. By this process rocks of different shapes and chemical composition were created.
Among the various kinds of alluvial deposits of these rocks, the so-called ignimbrites have a special meaning as the origin of porphyry. They originate from streams of fluid and gas-like mixtures with a depth of between 5 and 20 metres and possess a rather constant chemical composition. They form the so-called ignimbrite unity and reach a depth of several metres.
The currently processed porphyry is limited to one of these unities for which the vertical fissure and very clear breaks are characteristic. These qualities are essential for processing porphyry. As there is no formation of layers, the degradable depth is about 100-200 metres.
The chemical and mineralogical composition, as well as the typical porphyritic structure together with the formation of layers is responsible for these special qualities of porphyry such as increased breakthrough consistency, high chemical durability and high sliding and rolling friction. For this reason, porphyry is regarded as one of the most important materials for paving and surfacing in Europe.
Depending on the depth and length of the layer of the porphyry, cobblestones, floor slabs, irregular slabs, kerbstones, border stones, fishbone stones, masonry bricks, facing stones, steps and, after further processing, sawed, semi-polished, polished and flamed articles can be produced.