The stone extracted in the municipality of Cuasso al Monte is known under the commercial name of “Red Porphyry”, however petrographers have given the stone the modern name “granophyre”.

It is a volcanic hypoabyssal rock, chemically sialic, essentially composed of K-feldspar, quartz and biotite in a lower quantity.

The outcrop of the porphyry field extends nearly uninterruptedly to form a northeastward-southeastward area, from the western shore of the lake of Lugano until and even beyond the “Martica” mountain, at the border with the municipality of “Brinzio”. At certain points the single masses reach remarkable thickness and show an important erosion resistance (a clear example is given by the rough morphology of “Cavalizza” valley, east of the municipality of Cuasso al Monte, with its very steep walls and spurs).

Rock structure is made of porphyry with big crystals plunged into a finer grained mass which is the result of a solidification process which took place in two phases: the first one was slow and brought to crystallization (formation of crystals of big dimensions), the latter was faster and for this reason the remaining part of the melted rock had no time to crystallize completely. Normally the grain is middle, but you can often find zonings and ribs showing big pegmatite grains.

The granophyres of Cuasso al Monte are characterized by the presence of cavities due to the shrinkage of the magmatic mass during its cooling : these cavities are called “miarolic cavities “ and they can have different dimensions, from few mm up to a 5 cm diameter. The miarole inner surface is always full of well visible crystals such as potassic feldspars (orthoclase, microclyn), quartz, plagioclase (albeit, oligoclase), miche (biotite, muscovite), apatite, amphiboles, molybdenite, fluorite, topaz. One the contrary, there are fewer geodes, that is cavities of bigger dimensions between 10 and 70 cm.

In the whole granophyres surroundings, there are several Pb and Ag mineralization, which have often become economically important and have been miningly exploited (Miriva company in Val Ganna and in Marzio, not far from Cuasso al Monte). The dating of the formation period of the granophyres of Cuasso al Monte, calculated with the method Rubidio/Stronzio, has indicated an age of 275±8 Ma. More recent chemical analysis of the samples have indicated the total composition of the rock that, according to the oxide percentage of the most present elements, gives the following result: