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Lookout Mountain is a rhyolite dome that began to form 600,000 years ago after the cataclysmic eruption from the Long Valley Caldera. This eruption left much of what is now southern Mono County under a mantle of rhyolitic lava and ash. Some of the material ejected from the dome's 15 volcanic vents was obsidian: volcanically-formed glass which was prized by the basin's earliest inhabitants for making razor-sharp tools and for fashioning into objects of ceremony and beauty.

Obsidian has been quarried and traded for millennia by the area's Native Americans. Evidence of this quarrying and tool making are present all about the summit of Lookout Mountain in the form of roughly fractured obsidian boulders and cobbles and thousands of flakes: discarded material left in the process of producing rough outs and tools. Common tools made of obsidian were blades, projectile points, and scrapers. Desired by other Native American groups east and west of the Sierra, obsidian was an important trade item and commonly found its way hundreds of miles from its source at Lookout Mountain.

Lookout Mountain is located off of U.S. 395, between the towns of June Lake and Mammoth Lakes. It is reached via a short ascent on dirt roads 3S06 and 2S02, also known as the Lookout Mountain Road; a sign on the crest outlines the mountain's history. You will pass Obsidian Dome along the way.

Mammoth Lakes Visitors Bureau

Mammoth Ranger Station and Visitors Center
Highway 203, PO Box 148 Mammoth Lakes, CA 93546

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