ArrowPoint
Medicine Lake Highland obsidian, photo 1
Photo: James St. John, CC BY 2.0, via Wikimedia CommonsLicense (opens in a new tab)Photo source (opens in a new tab)

Named stone

Medicine Lake Highland obsidian

Also called Glass Mountain obsidian, Grouse Hill obsidian, Little Glass Mountain obsidian, Crater Glass Flow obsidian

A kind of obsidian

Medicine Lake Highland obsidianObsidianWest Coast & Plateau

2 photos

Description

The Medicine Lake Highland in northern California's Siskiyou and Modoc counties holds more than ten obsidian sources of seven chemical types, according to the Nevada Department of Transportation's source guide. Glass Mountain, listed as a huge, high-quality obsidian flow, has many local names, including Glass Mountain North and South, Little Glass Mountain, Grouse Hill and Crater Glass Flow. Other localities include Yellowjacket (gray to black banded glass with clear streaks, found below an ash layer) and Grasshopper Flat (milky gray and banded). An archaeological report on Colusa County foothill sites found Medicine Lake obsidian mixed with Borax Lake, Napa Valley and Mount Konocti glass. The opened sources do not give geology details.

How to identify it

Colour
Gray to black banded with clear streaks at Yellowjacket; milky gray and banded at Grasshopper Flat (Moore).
Texture
Glass Mountain is called a huge, high-quality obsidian flow.

Geology

Obsidian flows of the Medicine Lake Highland: more than ten sources of seven geochemical types. The opened sources give locations and names but not a geologic description; the USGS Medicine Lake page was blocked.

Where it comes from

West Coast & Plateau

States

Quarries and outcrops

  • Glass Mountain flows, Medicine Lake Highland
  • Yellowjacket and Grasshopper Flat localities
  • Modoc and Siskiyou counties

Used by

  • Archaic: Medicine Lake glass in Colusa County foothill sites with Borax Lake and Napa Valley glass (Bouey in Slaymaker 1983, as cited by White and others 2009)

Look-alikes

Stones that are easy to confuse with Medicine Lake Highland obsidian.

  • Tuscan obsidian (northern Sacramento Valley)
  • Other northern California sources (Borax Lake, Napa Valley, Mount Konocti)

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. Northwest Research Obsidian Studies Laboratory. California Obsidian Sources: Glass Mountain (source reference sheet).sourcecatalog.com (opens in a new tab)
  3. White, Gregory G., and others. 2009. Sites Reservoir Archaeological Inventory Report: cultural setting (Appendix 22A, Sites Project RDEIR/SDEIS). Archaeological Research Program, California State University, Chico.sitesproject.org (opens in a new tab)

All materials