Porphyry Gallery

Fragmentary head (porphyry)

1216478 Fragmentary head (porphyry) by Byzantine; height: 21.5 cm; Ashmolean Museum, University of Oxford, UK; (add.info.: Fragmentary porphyry head of a man wearing the diadem denoting an Augustus rather than a Caesar; the head is broken down its left side diagonally.); A© Ashmolean Museum ; out of copyright

© © Ashmolean Museum / Bridgeman Images

Porphyry Mine in Lessines, Belgium

Mine / Quarry for Porphyry at Lessines, Belgium. Porphyry is a variety of 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 brownish purple igneous rock with large crystals of plagioclase. This rock was prized for various monuments and building projects in Imperial Rome and later

© Mary Evans Picture Library 2015 - https://copyrighthub.org/s0/hub1/creation/maryevans/MaryEvansPictureID/10285145

Wherry Mine, Mounts Bay, Penzance, Cornwall, England. Wooden trestle bridge

Wherry Mine, Mount's Bay, Penzance, Cornwall, England. Wooden trestle bridge carrying the horizontal rods from the steam engine, left, to pump in the coffer dam at the end of the trestle which protected the shaft of the mine which was only uncovered at low water. Opened in 1781 to exploit a vein of quartz-feldspar porphyry, the mine was destroyed in 1798 when a ship in a storm destroyed the trestles and the coffer. Engraving from Transactions of the Royal Geological Society of Cornwall, 1818

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