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Obsidian Cliff obsidian, photo 1
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Named stone

Obsidian Cliff obsidian

Also called Yellowstone obsidian, Obsidian Cliff, Yellowstone National Park

A kind of obsidian

Obsidian Cliff obsidianObsidianRockies & Great Basin

2 photos

Description

Obsidian Cliff, a National Historic Landmark in Yellowstone National Park, is the benchmark Rocky Mountain obsidian. It stands beside the Grand Loop Road between Mammoth and Norris with about 98 feet (30 m) of exposed glass, unlike most obsidian, which lies as small rocks among other rocks. People first quarried it more than 11,000 years ago, taking it from the bedrock and from cobbles in the glacial till on top. The National Park Service calls it the most widely dispersed obsidian source used by hunter-gatherers in the United States, found along trade routes from western Canada to the Great Lakes and Ohio. About 90 percent of the obsidian in Hopewell burial sites of the Ohio River Valley (about 1,850 to 1,750 years ago) came from here. Wyoming study sites also depended on it, together with Bear Gulch and Malad.

How to identify it

Texture
Higher-quality glass than other Yellowstone-area sources: archaeologists explain its heavy use and long transport by that quality (MacDonald and others, as summarized in Pink 2023).

Geology

A thick body of natural volcanic glass forming a cliff in Yellowstone, formed where silica-rich magma cooled without growing crystals. The cliff exposes about 30 m of glass. The plateau above is mantled with glacial till containing obsidian cobbles. A 1988 fire cleared the surface and allowed new archaeological survey.

Where it comes from

Rockies & Great Basin

States

Quarries and outcrops

  • Obsidian Cliff, Yellowstone National Park (Grand Loop Road, between Mammoth and Norris)
  • Glacial-till cobbles on the Obsidian Cliff plateau

Used by

  • Clovis and earliest use: quarried more than 11,000 years ago
  • Hopewell: about 90 percent of obsidian in Ohio River Valley Hopewell mortuary sites, about 1,850 to 1,750 years ago (NPS)
  • Wyoming and northern Colorado sites: one of the three most important sources (Smith 1999)

Look-alikes

Stones that are easy to confuse with Obsidian Cliff obsidian.

  • Bear Gulch obsidian (compositionally similar; this is how the Bear Gulch source was first suspected to be near Yellowstone)
  • Cougar Creek obsidian (lower quality, Yellowstone Plateau)

Sources

  1. National Park Service. Obsidian Cliff. Yellowstone National Park.nps.gov (opens in a new tab)
  2. Smith, Craig S. 1999. Obsidian Use in Wyoming and the Concept of Curation. Plains Anthropologist 44(169).archaeologycolorado.org (opens in a new tab)
  3. Pink, Jeremias. 2023. The geology, geochemistry, and geographic distribution of southern Idaho obsidian: A provisional context for archaeological provenance research at the INL CRMO. INL/RPT-23-73575, Idaho National Laboratory.inldigitallibrary.inl.gov (opens in a new tab)

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