Porphyry has several qualities, which differentiate it from every other material and make it one of the most suitable rocks for any uses: among those

A very important characteristic: thank to the hardness of the materials it is composed of, porphyry is of one the most suitable materials for internal and external paving
Its wear resistance is particularly important in outside paving (especially streets) exposed to high sliding friction which usually over time tends to modify the original surface of the material.
Unlike other volcanic rocks (granites) porphyry does not get smooth due to wear or slippery when it rains.

 

Porphyry is highly resistant both to heavy loads and low temperatures. It is therefore a very suitable material for all kinds of facing and paving (with cubes, tiles, irregularly shaped slabs, having rough or polished surfaces) in houses, gardens, streets, squares and industrial plants since its resistance to freezing, its elasticity and impermeability make it almost unbreakable.

A very important quality of porphyry which makes it suitable to be used in chemical plants and iron foundries where materials are subject to very difficult conditions. Porphyry pavings are more resistant than ceramic ones, are not slippery and don't get soaked like cement ones.

The colour of porphyry depends on the kind of iron contained in it: some kinds of porphyry have darker shades going from green to black, whereas others are lighter going from grey to blue-grey and to red. In coverings of façades and in facings of supporting walls beautiful effects can be obtained by putting together stones with different colours and tonalities, whereas the nicest optical solution for pavings is the mixing of homogeneous material with material rich in contrasts.
Porphyry is a natural stone whose beauty is due to its numerous colour shades. (see Colour shades of porphyry )

That's why porphyry is never homogeneous in colour and this has to be taken into account when ordering it: the consigned material could present differences in its colour (as well as in its thickness).
These differences in colour (so typical in porphyry) are not only accepted but they are also considered as a natural quality of this stone.

Looking at porphyry from a geological point of view makes it easy to understand the qualities of this material and the reasons why it is by far the best one for street paving and generally in the building sector.
The formation of porphyry began about 250 million years ago in the Lower Permian period, when volcanic activity carried on for several million years, alternating between phases of eruptions and inactivity: The result was the creation of a "porphyry platform", an enormous complex of volcanic rocks in the Italian region "Trentino Alto Adige", extending from the "Val di Sesto" in the Pusteria area to Broccon Pass and from Idro Lake to Meran.

These rocks, which differ greatly in their chemical composition and formation, are the result of intense volcanic activity, which developed with linear eruptions through numerous fractures.
From a chemical point of view porphyry is made up of about 70% silica, 14% alumina, 8% alkali and small percentages of other substances, whereas from a mineralogical point of view it consists of several minerals, quartz being the prevalent one. The most outstanding characteristic of Trentino porphyry (which makes it very competitive on the natural rocks market and suitable for any kind of works) is its vertical stratification in almost parallel plans, whose thickness can vary from 1 to 50 cm.
No conclusive explanation has yet been found for this particular stratification, which allows for porphyry to be easily extracted: some people say it has a tectonic origin, whereas for others it is connected with the cooling of the lava.