El pórfido (en latín, porphyra, "piedra púrpura") es una roca filoniana denominada así por los romanos debido a su color, y que fue usada como signo de distinción. Es a al vez una piedra con una larga historia de uso como material decorativo.

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Porphyry is a textural term for an igneous rock consisting of large-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate rich, generally aphanitic matrix or groundmass. The larger crystals are called phenocrysts. In its non-geologic, traditional use, the term porphyry refers to the purple-red form of this stone, valued for its appearance. The term porphyry is from Ancient Greek (πορφύρα porphúra) and means "purple". Purple was the color of royalty, and the "imperial porphyry" was a deep purple igneous rock with large crystals of plagioclase. Some authors claimed the rock was the hardest known in antiquity. "Imperial" grade porphyry was thus prized for monuments and building projects in Imperial Rome and later. Subsequently, the name was given to any igneous rocks with large crystals. The adjective porphyritic now refers to a certain texture of igneous rock regardless of its chemical and mineralogical composition. Its chief characteristic is a large difference in size between the tiny matrix crystals and the much larger phenocrysts. Porphyries may be aphanites or phanerites, that is, the groundmass may have invisibly small crystals as in basalt, or crystals easily distinguishable with the eye, as in granite. Most types of igneous rocks display some degree of porphyritic texture.

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