Auteur: James St. John
Beschrijving:
Obsidian in perlite from the Miocene of Arizona, USA.
Perlite is a usually-gray, hydrated, rhyolitic, glassy rock. It forms by aqueous alteration of obsidian, a usually-black, rhyolitic, glassy rock. Seen here is a nodule of black obsidian in gray perlite matrix. The obsidian is unaltered - it's the original rock. Most of the rock has been hydrated into perlite. Obsidian nodules from the Superior, Arizona area are nicknamed "Apache tears".
Stratigraphy: Arnett Rhyolite Member, Picketpost Mountain Formation, Gila Group, Miocene, ~15 to 18.6 Ma
Locality: attributed to the "Imerys Perlite Quarry", near the town of Superior, northern Pinal County, southeast-central Arizona, USA
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