Tosawihi chert

Also called Tosawihi opalite, Tosawi chert, White Knife quarries chert, Battle Mountain opalite

Tosawihi chertChert (and flint)Rockies & Great Basin

Description

Tosawihi is a huge deposit of hydrothermally altered volcanic ash in Elko County, Nevada, and was the major non-obsidian toolstone of the Great Basin. The Nevada Department of Transportation says it is reputedly the reason the White Knife Shoshone got their name. The raw rock is granular, tough and durable and occurs in big ledges and blocks, so quarrying was hard; people used boulder hammerstones, wedges and fire. Once reduced to slabs and rough bifaces it can be heat-treated by burying it under a campfire. The colour changes, new flake scars look glossier, mercury or cinnabar may give a pink tint, and the stone flakes more evenly. A Bureau of Land Management report on five Little Boulder Basin sites confirms that Tosawihi chert dominates assemblages in that area, mostly as bifaces.

How to identify it

Texture: Granular, very durable and tough in the raw state; occurs in large ledges and blocks (Moore).
Luster: More lustrous after heat treatment.
Heat treatment: Experiments show slabs and rough bifaces can be heat-treated by burying them about 8 to 20 cm under a campfire for a few hours or overnight. Colour changes noticeably, new flake scars are glossier, the stone is easier to work and more homogeneous, but slightly less durable. Mercury or cinnabar tends to give a pink colour. Untreated stone suits knives and rough tools; treated stone suits pressure flaking and projectile points (Moore).

Geology

A huge deposit of hydrothermally altered volcanic ash (opalite), also described as chert, opalite and meta-quartzite, near Battle Mountain in Elko County, Nevada. A gold mine was blasting it to reach the gold below when Moore wrote.

Where it comes from

Rockies & Great Basin

States

Nevada

Quarries and outcrops

Tosawihi / Tosawi quarries, Elko County, Nevada (near Battle Mountain)
Little Boulder Basin, Eureka County, Nevada (nearby archaeological sites)

Used by

White Knife Shoshone (named for the quarries, per Moore)
Great Basin hunter-gatherers: bifacial reduction of Tosawihi chert at Little Boulder Basin sites, indicating high mobility (BLM report)

Look-alikes

Stones that are easy to confuse with Tosawihi chert.

Other Great Basin cherts and obsidians (obsidian makes up only a small share of the Little Boulder Basin assemblages)

Sources

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)
Bureau of Land Management, Nevada. Data Recovery Excavations at Five Prehistoric Archaeological Sites in the Little Boulder Basin, Eureka County, Nevada. SWCA Environmental Consultants report for Barrick Goldstrike Mines.blm.gov (opens in a new tab)

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