Corsi Collection of Decorative Stones

view of stone 783

Corsi 783, approx. 145 x 73 x 40 mm, © Oxford University Museum of Natural History

OUMNH Number: 783  
Name and quarry location: Imperial porphyry, porfido rosso antico, from Gebel Dokhan, Eastern Desert, Egypt  
Geological description: Andesite-dacite porphyry with pink phenocrysts of plagioclase feldspar. The purple colour is due largely to trace piemontite, the manganese member of the epidote group, and indicates a degree of metamorphism. It is from the Precambrian basement rocks.  
Comments: This is a very typical example of the imperial porphyry from Gebel Dokhan (the ancient Mons Porphyrites) in the Eastern Desert of Egypt. The geological term 'porphyry' for rocks with larger crystals in a fine-grained groundmass, comes from this rock which is itself named from the Latin for purple. The imperial quarries were worked from at least the 1st century through to the 5th century AD, using a workforce of slaves. The ancient quarries were rediscovered in 1823, and their location was described by the quarry hunter William Brindley (1887). They were never reopened on a commercial scale, so virtually every example of this stone seen around the world was quarried in ancient Roman times.  
References: Borghini (1997) 274; Brindley (1887); Corsi (1845) 200-204; Harrell (2010a); Lazzarini (2002c) 233-235; Mielsch (1985) 64-65, taf.21; Price (2007) 202-203; Rogers (2008) 45-47  
Further information:

Corsi's classification: Class 15. Porphyry; Species 1.; i. Antique porphyry  
Corsi's text: 193.1 Porfido antico. Marmor Porphyrite. Porfirite. Porfido rosso... la prime cave del porfido rosso si aprissero presso l'istmo di Sues. Di altra cave di porfido aperta nella Tebaide... si è chiamata Tebano. Marmo Romano  

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