"Porphyry (/ˈpɔːrfəri/ POR-fə-ree) is a textural term for an igneous rock consisting of coarse-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 the Ancient Greek πορφύρα (porphyra), meaning "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. Thus, "imperial"-grade porphyry was prized for monuments and building projects in Imperial Rome and thereafter. " - (en.wikipedia.org 10.04.2022)
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