Corsi Collection of Decorative Stones

view of stone 704

Corsi 704, approx. 145 x 73 x 40 mm, © Oxford University Museum of Natural History

OUMNH Number: 704  
Name and quarry location: Amazon stone, from Russia; most probably from Miass, Chelyabinsk Oblast.  
Geological description: Amazonite or amazon stone, a variety of microcline feldspar.  
Comments: The specimen is a composite cut from large crystals/crystalline masses, and is almost certainly from near Miass, Ilmen Mountains, Russia. The fine crystals from Virginia and Colorado, USA, the best known sources of amazonite in the 19th century, were not known in Corsi’s time. Amazonite is not known to come from the area of Brazil around the Amazon river. Amazonite is a pegmatite mineral that derives its colour from trace lead, not copper. The scale-like appearance to which Corsi refers is a very characteristic feature of this stone and is where the mineral has crystallised into separate areas of white albite (sodium feldspar) within the green microcline (potassium feldspar).  
References: Corsi (1845) 257-259; De Graaf (2006); Watson (1916) 389-90; Webster (1994) 211-212; Price (2007) 260; Zeitner (1996) 187  
Further information:

Corsi's classification: Class 13. Feldspars; Species 1. Amazon stone  
Corsi's text: 169 Pietre delle Amazzoni. Smaragdum calchedonium. smeraldi, chiamata delle Amazzoni perchè trovato presso quel fiume in America.  

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