Porphyry is a textural term for an igneous rock consisting of large-grained crystals such as feldspar or quartz dispersed in a fine-grained feldspathic 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 Greek and means “purple”. Purple was the color of royalty, and the “Imperial Porphyry” was a deep purple igneous rock with large crystals of plagioclase. The rock was the hardest known in antiquity and was prized for monuments and building projects in Imperial Rome and later.
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