Information about porphyry

Historical background

Porphyry is a particular type of volcanic rock which in this case comes from the so-called “Adige porphyry shelf”, an enormous sheet of volcanic rock that stretches out in the Trentino Alto Adige region. The rock, very varied and different in terms of both its chemical composition and its method of formation, is the result of intense volcanic activity, which took place with linear eruptions along numerous fractures, beginning 260 million years ago during the early Permian period and continuing for several million years, with continuously alternating phases of eruption and lulls in activity.

The deposits of so-called ignimbrite are of particular importance as they led to the formation of “porphyry”.

Ignimbrite is a deposit of liquid-gassy flows with thicknesses generally varying from 5 to 20 metres and with relatively constant chemism, resulting in the forming of the so-called ignimbrite unit, which reaches a thickness of hundreds of metres.

The porphyry currently worked is limited to one of these ignimbrite units (classified as rhyolitic ignimbrite), characterised by vertical fissuring and by very clean percussion fractures, indispensable for the working of porphyry; the workable thickness is around 100-200 metres, given the absence of layering.

Applications

When one has the opportunity to admire the square in an important city, take a walk in the historic centre of a village or contemplate the cladding of a building of architectural merit, relatively frequently one can observe that the material adopted is porphyry, in particular exclusive Trentino porphyry.

Products made with Trentino porphyry can be adapted for a wide variety of purposes and are therefore adopted both for external paving and internal flooring of particular refinement and for the cladding of walls and buildings. The versatility of this material allows any type of product to be created, making it possible to satisfy every possible architectural requirement.

Porphyry is a natural stone, its appeal deriving from the different colour variations.

The colour depends on the type of iron present: there is indeed darker rock verging on green or black and paler coloured rock going from grey or greyish blue to red.

For this reason the different shades are never identical: indeed the material delivered may vary both in terms of the colour and the thickness. The difference in colour is typical of porphyry and is generally considered to be tolerable as it is a characteristic of natural stone.