rhyolite - hydrothermally altered rhyolite associated with gold mineralization - display specimen

Textbook display specimen of hydrothermally altered rhyolite from the Monte Cristo Range in Nevada. Initially a light tan, this rhyolite was brecciated by faulting and then hydrothermally altered, with the mineralizing fluids rising through fractures in the breccia and permeating the rhyolite.

Banding was caused by changes in the chemical composition of the mineralizing fluids.  Later displacement of the fractures breaks the mineralized bands. An interesting example.

This rhyolite was associated with gold mineralization, and was exposed during development of the Boss Mine in Esmeralda County, which recovered gold by heap leaching cyanidation. 

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