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Named stone

Casa Diablo obsidian

Also called Lookout Mountain obsidian, Sawmill Ridge obsidian, Prospect Ridge obsidian

A kind of obsidian

Casa Diablo obsidianObsidianWest Coast & Plateau

Description

Casa Diablo, in Mono County on the east side of the Sierra Nevada near Crowley Lake, is a major obsidian source with several quarry localities, including Lookout Mountain, Sawmill Ridge and Prospect Ridge. At Lookout Mountain the glass forms ledges several meters thick that dip steeply and are fractured like a three-dimensional jigsaw puzzle, with many fractures lined with ash, so some of it is unusable while some is quite good. It is chemically identical to Casa Diablo two miles south. Archaeologists find Casa Diablo glass across the Sierra to the west. It dominates obsidian at sites in the west-central Sierra Nevada and the central San Joaquin Valley, and it was part of a trade system that moved eastern California obsidian westward from about 4,000 years ago.

How to identify it

Texture
Some of the Lookout Mountain material is so fractured it cannot be used; some is quite good.
Inclusions
Lookout Mountain glass tends to have many fractures lined with ash (Moore).

Geology

Obsidian outcrops and nodules west of Crowley Lake, Mono County, eastern California. At Lookout Mountain the ledges are several meters thick and dip steeply to the north; uplift fractured them into jigsaw-like blocks. The Lookout Mountain glass is geochemically identical to Casa Diablo two miles south.

Where it comes from

West Coast & Plateau

States

Quarries and outcrops

  • Casa Diablo, west of Crowley Lake, Mono County
  • Lookout Mountain, southeast flank, about 5 miles south of Mono Lake (outcrops and nodules)
  • Sawmill Ridge and Prospect Ridge localities

Used by

  • Trade west across the Sierra Nevada: obsidian from eastern California quarries traded to the Sierra and San Joaquin Valley beginning about 4,000 years ago (Ericson model, summarised by Sutton and Des Lauriers)
  • By the Late Horizon (about 1,500 B.P.), Casa Diablo and Bodie Hills use had decreased as small arrow points replaced large bifaces (Ericson, as cited by Sutton and Des Lauriers)

Look-alikes

Stones that are easy to confuse with Casa Diablo obsidian.

  • Bodie Hills obsidian (the other main eastern California source in San Joaquin Valley assemblages)
  • Coso obsidian (dominates the southern valley)

Sources

  1. Moore, Joe. 2009. Great Basin Tool-Stone Sources: The NDOT Obsidian and Tool-Stone Sourcing Project, 2002 Progress Report. Nevada Department of Transportation, Cultural Resource Section.deschutesmeridian.com (opens in a new tab)
  2. Sutton, Mark Q., and Matthew R. Des Lauriers. 2002. Emerging Patterns in Obsidian Usage in the Southern San Joaquin Valley, California. Pacific Coast Archaeological Society Quarterly 38(2-3).pcas.org (opens in a new tab)
  3. Northwest Research Obsidian Studies Laboratory. California Obsidian Sources: Casa Diablo (source reference sheet).sourcecatalog.com (opens in a new tab)

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