Cristobalite & Fayalite in Obsidian (Mullane Coll.)

Item Description

"Eyes" of oxidized and unoxidized high-temperature cristobalite are nicely set in both sides of the highly lustrous, razor-sharp, jet-black obsidian on this visual and sculptural specimen from an obscure California locale - Obsidian Ridge, Inyo County. The "eyes" reach 2.9 cm. Obsidian (volcanic glass) cools too quickly, to crystallize. Thus, it is unusual to see minerals attached. The "eye" or sphere of high temperature cristobalite (SiO2) is actually the result of devitrification, or loss of silica from the obsidian. The two "eyes" on the back each host a small glassy olive-green fayalite blade, an Olivine Group mineral. Certainly, a most unusual and uncommon specimen! Very rare, older material from this uncommon locale. The faded R.M. Wilke label dates from 1907 to the early 1940s. Ex Dennis Mullane Collection.