Cristobalite and Fayalite in Obsidian (Burton Jurgl & Ydren Coll.)

Item Description

A visual and showy specimen of a "eyes" of high-temperature cristobalite nicely set in highly lustrous, jet-black obsidian from an uncommon California locale - Coso Hot Springs, Inyo County. The large, 2.5 cm "eye" has scattered crystals of gemmy, olive-green, micro-blades of fayalite, an olivine group mineral. Obsidian (volcanic glass) cools too quickly, to crystallize. Thus, it is unusual to see minerals attached. The "eyes" or spheres of high temperature cristobalite (SiO2) are actually the result of devitrification, or loss of silica from the obsidian. Certainly, a most unusual and uncommon specimen! Very rare, older material from this uncommon locale, dating to the 1950s or 60s. Ex Burton Jurgl and John Ydren Collections.