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Named stone

Potter chert

Also called Potter quartzite, Potter member quartzarenite, Ogallala gravel quartzite (in part)

A kind of quartzite

Potter chertQuartziteTexas & Southwest

Description

Potter chert is not a true chert. Archaeologists in the Texas Panhandle use the name for fine-grained, silica-cemented siltstone and quartzite cobbles from the outwash gravels at the base of the Ogallala Formation, the Potter member. It is the most distinctive stone in those gravels, which also hold quartzite, jasper, siltstone, chalcedony, opalite and silicified wood. It is mostly green or red, though heating changes the colour, and grain size ranges from very coarse to very fine. Because the cobbles are easy to pick up across the Canadian River valley and much of the Panhandle, it was used mostly for big chopping, cutting and pounding tools and crude bifaces, and as hearthstones, rather than fine points.

How to identify it

Colour
Mostly green or red; heat treatment changes the colour (Quigg et al. 2010). Also described as often reddish or greenish, and weathered pieces as greenish grey (Quigg et al. 2010).
Texture
Grain size ranges from extremely coarse to very fine (Quigg et al. 2010). Very well-indurated quartzose sandstone (Hurst 2024).
Heat treatment
Heating alters its colour (Quigg et al. 2010).

Geology

Cobbles in the basal outwash gravels of the Ogallala Formation, called the Potter member, a very well-indurated quartzose sandstone (Hurst 2024). Holliday and Welty (1981), as summarised by Quigg et al. (2010), class it as a fine-grained silica-cemented siltstone.

Where it comes from

Texas & Southwest, Plains

States

Quarries and outcrops

  • Ogallala gravels of the Canadian River valley and much of the Texas Panhandle (Quigg et al. 2010)
  • Basal Ogallala gravels near Post, Garza County, on the eastern escarpment of the Southern High Plains (Hurst 2024)

Used by

  • Late Archaic and later sites on the Landis Property, Potter County, Texas (about 4.6 percent of debitage at one site; bifaces and choppers) (Quigg et al. 2010)
  • Late Archaic of the Texas Panhandle region: in the report's regional summary (its Table 3-2), most tools (58 percent) are on local stone, with Potter chert at 48 percent, while Alibates and Tecovas make up only 16 percent (Quigg et al. 2010)
  • Used across the Great Plains for tools and as hearthstones (Hurst 2024)

Look-alikes

Stones that are easy to confuse with Potter chert.

  • Ogallala quartzite (orthoquartzite from the same formation; see the Ogallala quartzite page)
  • Tecovas jasper and quartzite and Alibates agatized dolomite, the fine Panhandle stones found with it (Quigg et al. 2010)

Sources

  1. Quigg, J. Michael, Charles D. Frederick, Paul M. Matchen, and Kendra G. DuBois. 2010. Landis Property: Data Recovery at Three Prehistoric Sites (41PT185, 41PT186, and 41PT245) in Potter County, Texas. Volume I. TRC Report No. 150832, TRC Environmental Corporation, Austin, for the Bureau of Land Management, Amarillo Field Office (posted by Texas Beyond History).texasbeyondhistory.net (opens in a new tab)
  2. Hurst, Stance. 2024. Rough and Tumbled: The Geoheritage Significance of Ogallala Formation Quartzarenite Clasts in Northwestern Texas. Abstract, Geological Society of America Connects 2024, Anaheim.gsa.confex.com (opens in a new tab)

All materials