Obsidian glass, near Bend, Oregon

&lt;p&gt;It is relatively rare to find extensive exposures of obsidian glass, but the Big Obsidian Flow provides such a feature. &amp;nbsp;Cooling was so rapid that crystallization was prevented. &amp;nbsp;Like all glass, this rock displays perfect conchoidal fracture surfaces, of the type that also characterizes flint and chert when worked.&lt;/p&gt;

Whereabouts

I collected this in the mid-1990s while on vacation. What I vividly recall is the razor-blade sharpness of the glass, and paying the price of blood for grabbing a piece. I like the jet black color and the perfect conchoidal fracture features.

Age & Formation

1300 years B.P., the Big Obsidian Flow of the Newberry Volcano.