Corsi Collection of Decorative Stones

view of stone 667

Corsi 667, approx. 145 x 73 x 40 mm, © Oxford University Museum of Natural History

OUMNH Number: 667  
Name and quarry location: Lava di Borghetto, from Borghetto, Civita Castellana, Viterbo, Lazio, Italy  
Geological description: Phonolite tephrite. A porphyritic rock with euhedral white megacrysts of leucite and scattered black pyroxene crystals in a fine-grained groundmass. The leucite megacrysts are cracked, sometimes concentrically zoned, and contain inclusions of pyroxene.  
Comments: The big round leucite crystals, typically fractured and often filled with the same fine-grained groundmass that surrounds them, are the characteristic features of the volcanic lava that has been extracted in the area of Borghetto since Roman times, and was extensively used for paving slabs.  
References: Faramondi (1985) 8-13, 18-19; Price (2007) 212  
Further information:

Corsi's classification: Class 8. Volcanic stones; iii. Stones from extinct volcanoes  
Corsi's text: 157.1 Lava di Borghetto presso Civita Castellana  

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