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Porphyry

An igneous rock characterized by porphyritic texture, in which large crystals (phenocrysts) are enclosed in a matrix of very fine-grained to aphanitic (not visibly crystalline) material. Porphyries are generally distinguished from other porphyritic rocks by their abundance of phenocrysts and by their occurrence in small intrusive bodies (dikes and sills) formed at shallow depth within the earth. In this sense porphyries are hypabyssal rocks.

Porphyries occur as marginal phases of medium-sized igneous bodies (stocks, laccoliths) or as apophyses (offshoots) projecting from such bodies into the surrounding rocks. They are also abundant as dikes cutting compositionally equivalent plutonic rock, or as dikes, sills, and laccoliths injected into the adjacent older rocks.

Porphyry is different than granite, which cooled from its molten state into mainly solid formations, in that as it cooled, it fractured in both vertical and horizontal fissures.

Porphyry is made up of over 70% silica, about 14% alumna, 8% alkali and small percentages of iron, calcium and magnesium. Its mineral composition is quartz, sanidine and plagioclase crystals, biotite and pf pyroxenes in a vitreous paste. 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, America and around the world.

Porphyry Material

Porphyry has an even yet rough surface and, thanks to the difference in hardness of the minerals it contains, Porphyry Pavers do not become smooth due to wear or slippery when it is wet. It is ideal for commercial and residential use due to its durability.

Porphyry is an excellent choice of materials for facing outdoor surfaces as it is unaffected by freezing and thawing and because of its high resistance to chemicals. It is particularly recommended for public areas, including plazas, sidewalks, pool decks, fountains and parks.

Porphyry has extremely low maintenance costs, as proved by the excellent conditions of many roads and squares paved hundreds of years ago throughout the world.

The increase in the concern for safety and durability has led to the adoption of protective surfaces which resist and prevent slipping, are impermeable, are easy to repair, have minimal installation and maintenance costs, and offer and offer an economic solution because of its durability.

Material Notes:
Porphyries are igneous rock types with a mixed texture and grain size 1- 3 mm (hypabyssal). They are acidic, with a total silica content greater than 65%.

See also: The Royal Stone - Porphyry By Kate Parrott ; Porphyry Introduction ; About Porphyry

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