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Sioux quartzite, 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

Sioux quartzite

Also called Sioux Formation quartzite

A kind of quartzite

Sioux quartziteQuartzitePlains

Description

Sioux quartzite is a very hard, cross-bedded quartzite about 1.5 to 1.75 billion years old that underlies southwestern Minnesota, southeastern South Dakota and northwestern Iowa, though it reaches the surface in only a few places. Its sand grains carry a film of hematite, so the rock looks reddish to grey. At Pipestone National Monument it forms the ridge that holds the thin catlinite beds, and quarriers still dig through several feet of it to reach the pipestone. It is a poor stone to flake. Pieces at sites in southwestern Minnesota are common but rarely show clean flake features, so it served mostly for pounding and other rough jobs. Its outcrops also carry pecked petroglyphs, and a pebble conglomerate at its base holds some flakeable quartz and jasper.

How to identify it

Colour
Reddish to grey; the colour comes from hematite coating the sand grains (NPS overview).
Texture
Very hard, dense, cross-bedded orthoquartzite of medium to fine quartz sand, more than 90 percent quartz (NPS overview). Fragments at sites usually lack clear flake features (Bakken; NPS overview).

Geology

Early Proterozoic orthoquartzite laid down by braided rivers, 1.5 to 1.75 billion years old and estimated at 1,000 to 3,000 m thick. Thin beds of siltstone, mudstone and claystone occur inside it; at Pipestone National Monument one of these claystones is catlinite. The beds dip 5 to 10 degrees east there (NPS overview). At some places its base is a conglomerate with pebbles and cobbles of quartz, jasper and other flakeable stone (Bakken).

Where it comes from

Plains, Midwest/Ohio Valley

States

Quarries and outcrops

  • Pipestone National Monument, Pipestone County, Minnesota (west-facing escarpment and quarry line)
  • Outcrops in the western part of Minnesota's Southern Resource Region (Bakken)
  • Bedrock under southwestern Minnesota, southeastern South Dakota and northwestern Iowa (NPS overview)

Used by

  • Woodland and Mississippian (Plains Village) peoples in the Rock River drainage used more Sioux quartzite than earlier peoples (Gibbon and Hruby 1983, summarised in the NPS overview)
  • Common in chipped-stone collections at Pipestone National Monument, mostly for expedient pounding tools (NPS overview)
  • Petroglyphs pecked into its outcrops (NPS overview; Bakken)

Look-alikes

Stones that are easy to confuse with Sioux quartzite.

  • Other quartzites from glacial drift in southern Minnesota (Bakken)
  • Hixton silicified sandstone (Wisconsin) and Bijou Hills silicified sediment (South Dakota), both better flaking stones

Sources

  1. Scott, Douglas D., Thomas D. Thiessen, Jeffrey J. Richner, and Scott Stadler. 2006. An Archeological Inventory and Overview of Pipestone National Monument, Minnesota. Midwest Archeological Center Occasional Studies in Anthropology 34. National Park Service, Lincoln, Nebraska.govinfo.gov (opens in a new tab)
  2. Bakken, Kent E. (written about 1995; PDF issued later). Chipped Stone Raw Materials. Chapter 6 in Stone Tools of Minnesota. Minnesota Office of the State Archaeologist, St. Paul.mn.gov (opens in a new tab)

All materials