4/6 cubes are particularly recommended for paving which are mainly subject to pedestrian traffic, for example roads and squares in town centres, courtyards, porticoes, pedestrian islands, pavements, garden paths.
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. This began 260 million years ago in the Lower Permian and carried on for several million more years, alternating between phases of eruptions and inactivity.
Porphyry comes from ignimbrites, which is a deposit in these rocks from the volcanic activity.
Ignimbrites are flows of gaseous-liquid mixtures between 5 and 20 metres thick with a rather constant chemical composition and which constituted the ignimbritic unit which is hundreds of metres thick.
At present porphyry is worked only in one of these units (classified as rhyolitic ignimbrite) characterised by very neat vertical fissuring and percussion fracturing which are necessary for working porphyry; because of the lack of stratification, it is possible to work a thickness of about 100-200 metres.
The chemical composition of porphyry (over 70% silica, about 14% alumina, 8% alkali and small percentages of iron, calcium and magnesium), its minerals composition (quartz, sanidine and plagioclase crystals with smaller amounts of biotite and of pyroxenes in a vitreous paste) and its distinctive structure, as well as stratification, determine porphyry's technical characteristics (high compression breaking point, high resistance to chemical agents, high sliding and rolling friction) which make it one of the most important materials for paving and facing in Europe.
Porphyry has a rough surface and, thanks to the difference in hardness of the minerals it contains, porphyry pavings do not become smooth due to wear or slippery when it rains. Porphyry is suitable for facing outdoor surfaces since it is unaffected by freezing and thawing. It is recommended in factories and foundries because of its high resistance to chemical reagents. It is also particularly recommended for public works, for example for constructing the banks of river bed and for building external walls and road embankment walls.
What's more, it has an extremely low maintenance cost, and this is proved by the excellent conditions of many roads and squares paved dozens of years ago.
The increase in road traffic has led to the adoption of protective coverings which are highly resistant to compression and sliding friction, which prevent slipping, are elastic, impermeable, easy to repair and inspect below ground, have a minimal installation and maintenance cost and are naturally the cheapest solution in relation to their hard wear. Porphyry fits all these requirements. According to the thickness and size of the stratum, porphyry can be worked into cubes, tiles, irregular slabs, kerbstones, binders, smolleri and rusticated ashlar, and by further workmanship into sawn, polished and semi-polished material.
Porphyry Cubes
Porphyry cubes are the most well-known form of porphyry. They come in four different sizes: 4/6, 6/8, 8/10 and 10/12. Their weight per square metre is 105, 135, 190 and 250 kg respectively.
4/6 cubes are particularly recommended for paving which are mainly subject to pedestrian traffic, for example roads and squares in town centres, courtyards, porticoes, pedestrian islands, pavements, garden paths.
6/8 cubes are instead recommended for paving roads subject to mixed traffic (pedestrian and motor traffic) both in urban centres and elsewhere. They have also proved extremely useful in zootechny for paving modern stables.
8/10 and 10/12 cubed are suitable for paving roads and squares subject to intense traffic, in urban centres and in industrial plants (blast-furnaces, foundries, chemical industries) where they are subject to knocks and heavy loads or where chemical substances are present - porphyry infact resists acid corrosion.
Porphyry cubes may be arranged in various ways and different geometrical patterns (contrasting arches, concentric circles, in the shape of a fan or a peacock tail) and are sometimes framed by porphyry of a different tone of colour. For successful paving it is important to use a good quality foundation which will guarantee a lasting laying.
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Porphyry Tiles
Porphyry tiles are used to pave kerbs, squares, roads in town centres, driveways, courtyards, porticoes, warehouses. They are of aesthetical value for paving and facing interiors (polished and semi-polished tiles) and for outer facings (house basements, load-bearing structures) with sawn or cut sides.
Tiles are particularly recommended for paving terraces since they are not slippery, even when they are wet. They can also be used for roadside ditches.
The tiles are made in the following sizes: width 10, 15, 20, 25, 30, 35, 40 cm; length variable, but never less than the width; thickness varying from 2 to 5 cm. Tiles with a set length are made on order.
Porphyry has an infinite number of uses, since it suits many different environments and is both functional and decorative. It is used by architects and town-planners to furnish and decorate simple cottages and country houses, or modern and refined residential buildings, or for public and private construction work. Porphyry's technical advantages remain unequalled and it has become one of the most sought-after materials.
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Porphyry Slabs
The cheapest kind of paving is made with irregular porphyry slabs opus incerta. The irregular slabs may be normal if 2-5 cm thick, or thin if less than 2.5 cm thick - both kinds measuring between 15 and 50 cm - or giant if 2-6 cm thick and larger sized. Normal slabs weight about 90 kg per m2, thin slabs weigh 60/75 kg per m2 and giant slabs weigh 100/120 kg per m2.
Porphyry has paved all the most beautiful squares in Europe and the world over. To mention but a few of them the olympic stadium in Munich, the main square in Frankfurt, the underground and market square in Paris, the Burghiba summer residence at Caltagirone, the military cemetery in Hawaii, the old city centre in Sydney - Australia, the central square in Geddah - Saudi Arabia, Kennedy airport in New York, the ENIT palace in the EUR district of Rome, the Exhibition Centre and the Certosa cemetery in Bologna.
Irregular slabs are also used for outer facings and for house basements. Irregular tiles are particularly suitable for paving squares, courtyards, pavements, pedestrian passages, driveways, garden paths. Thin slabs are recommended for paving terraces and raised surfaces because of their limited thickness and light weight.
Because of its rough surface this material is particularly useful for bordering swimming pools.
Porphyry is used in modern architecture to add a personal touch to open spaces and to give buildings an element of functionality and decoration.
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Porphyry Binders
Binders are used to border any type of paving, to mark road boundaries, to separate two different types of paving, to form squares, to form flower beds and gardens.
The smallest binders are 10 cm high and are used to border squares made with 4/6 - 6/8 cubes, slabs, tiles or other types of material. 12 cm binders are usually used to border pavements, squares, roads (Switzerland), to pave squares and roads (Switzerland, Germany), to form ditches around traffic islands, to border roads, to build steps, etc. Because they are so resistant and hard wearing, porphyry kerbs are more economical than cement kerbs, which are unaesthetic and less resistant.
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Porphyry Kerbstones
Porphyry kerbstones, which come in minimum widths of 5, 6, 7 and 8 cm, always prove to be most suitable for bordering flower-beds, garden paths, etc. The wider kerbstones, which come in maximum widths of 10, 12 and 15 cm, are used for pavements and flower-beds in built-up areas, public parks and sports centres or for building steps, traffic islands, etc. Porphyry kerbstones are worked in two different ways:
In levelled ribs (their upper surface is bushhammered, cut or sawn), or in sawn ribs (their upper surface is levelled).
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Porphyry Smolleri and Ashlar
Smolleri (small strips of slabs) placed flat one on top of the other are particularly suitable for facing walls, pillars and basements. Placed perpendicularly side by side they are used for paving steep sloping roads, particularly in areas subject to frosting and in garage approach ramps.
Rusticated ashlar is particularly suitable for building the banks of a river bed and for building retaining walls, external walls and road embankment walls. This precious material is used more and more in large construction work. It is also highly relied on for public works. The production of machine - cut rusticated ashlar - which is not as deep as previous types were - is also noteworthy.
Rusticated ashlar is available in the following sizes: height 10/15, 12/20 and 15/25 with variable width.
Porphyry is also used in modern construction work and in restoration work to face steps and risers, balconies and landings, thresholds, window-sills and door-frames. Massive porphyry steps - in which the thread and riser are made from the same piece of material - are also available.
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Worked Porphyry
Worked porphyry (which is sawn, polished or semi-polished) is particularly noteworthy and of aesthetical value. Tiles with sawn borders and levelled or sawn, polished or semi-polished surfaces, steps with sawn ribs and levelled, polished or semi-polished surfaces, sills, risers, skirting boards and bases, are available on order.
Because of its high resistance to temperature changes, acids, knocks and abrasions, porphyry is a unique and extremely hard wearing materials. Porphyry is also used for furnishing and decorative purposes, for example for making fireplaces, tables and benches.
Polished and semi-polished tiles may be used in any type of environment as they are both elegant and functional. They may be used indoors, particularly in premises subject to medium or intense traffic (for example lobbies, living-rooms, fireplace areas, traditional kitchens and bathrooms) or in reception rooms, waiting rooms (in airport or railway stations), public offices, church interiors, banks, in other words in any environment requiring a touch of prestige.
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