Corsi Collection of Decorative Stones

view of stone 712

Corsi 712, approx. 145 x 73 x 40 mm, © Oxford University Museum of Natural History

OUMNH Number: 712  
Name and quarry location: Amethyst, locality unknown  
Geological description: Amethyst, the purple variety of quartz, part of a vein or geode showing the typical colour zoning of the crystals described by Corsi.  
Comments: Amethyst is a common mineral, and Corsi’s specimens may have come from Oberstein (now Idar-Oberstein) in Germany, Schemnitz in Hungary (now Banská Štiavnica, Slovakia), or any of the other significant deposits of the time. Large geodes bearing fine amethyst crystals are today obtained from the basalts of Brazil and Uruguay, but these were not known in Corsi’s time. According to Nassau (1984), the violet to purple colour of amethyst is derived from trace ferric iron, not manganese.  
References: Bauer (1904) 481-488; Frondel (1962); Nassau (1984) 56; Price (2007) 239; Webster (1994) 225-229; Zeitner (1996) 66-68  
Further information:

Corsi's classification: Class 14. Quartz and its varieties; Species 2. Amethyst  
Corsi's text: 178.1 Amatista... Trovasi in molti luoghi.  

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