Rough-grade obsidian (volcanic glass) is exposed in this roadcut along the Rim Drive in Crater Lake National Park, Oregon.  It doesn't seem to be mentioned much in any general geological analysis of the park, but it is an interesting feature to see.  I have also found older obsidian exposed further north on the slopes of Middle Sister, Oregon.  The obsidian here is exposed in several sections along the Rim Drive on the north & west rim of the lake.