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Jasper, photo 1
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Rock type

Jasper

Also called Red jasper, Yellow jasper, Pebble jasper

Jasperjasper (iron-rich chert)All regions

Description

Jasper is chert coloured by iron: opaque, often waxy, and typically red, yellow, orange or brown, sometimes green. Its iron comes from different settings. Pelletal jasper replaced iron-rich limy mud on shallow tropical sea floors; Hardyston jasper of Pennsylvania formed when hot water replaced quartzite; banded iron formation jasper is laminated, brick red and softer than most. Heating generally makes jasper waxier and redder. Burial in tidal marsh can change surface colours so that jasper looks like plain chert, and jasper of one colour can come from many places, so a colour name alone says little about the source. Named sources include Hardyston (Pennsylvania) and Flint Run (Virginia).

How to identify it

Colour
Red, yellow, orange or brown from iron impurities; some jasper is green (reduced iron) or brick red (oxidised iron).
Texture
Fine grained, often waxy; banded iron formation jasper is finely laminated and may be crossed by quartz veins.
Luster
Often lustrous and waxy; banded iron formation jasper has a matte luster on fresh breaks but polishes.
Inclusions
Quartz veins or chalcedony coatings in some pieces.
Heat treatment
Heating generally makes jasper waxier and redder (Maryland guide).

Geology

Jasper is a colourful chert whose colour comes from iron. In the Gulf Coastal Plain gravels, pelletal jaspers derive from Paleozoic bedrock rocks that were iron-rich carbonate muds; red jasper has iron in an oxidised state and green jasper in a reduced state, and banded iron formation jasper comes from far north in the Mississippi watershed. Pennsylvania jasper is hydrothermal replacement of quartzite in the Hardyston Formation. Flint Run jasper formed where weathered silica-rich volcanic rock released iron oxide and silica that groundwater deposited in carbonates. Minnesota's jasper taconite is deep red with small round inclusions that look like ooliths.

Where it comes from

All regions

States

Quarries and outcrops

  • Hardyston Formation, Pennsylvania
  • Flint Run, Warren County, Virginia
  • Point of Rocks, Frederick County, Maryland, and Iron Hill, Delaware (named by the Maryland guide)
  • Pre-loess terrace and Mississippi River gravels, Mississippi
  • Jasper taconite, northeastern Minnesota and Ontario

Used by

  • Jasper was valued in the Middle and Late Archaic lower Mississippi Valley lapidary industry for its colour (MDEQ)

Look-alikes

Stones that are easy to confuse with Jasper.

  • Plain chert, especially after burial in tidal marsh (Maryland guide)

Sources

  1. Maryland Archaeological Conservation Laboratory. Jasper. Diagnostic Artifacts in Maryland: Common Stone Types (Jefferson Patterson Park and Museum).apps.jefpat.maryland.gov (opens in a new tab)
  2. Delaware Department of Transportation. Archaeology glossary.deldot.gov (opens in a new tab)
  3. Mississippi Department of Environmental Quality, Office of Geology. Lithic Materials (web page; updated December 2023).mdeq.ms.gov (opens in a new tab)
  4. 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)
  5. Ebright, Carol. 1999 (updated 2023). Pennsylvania Jasper. Virginia Department of Historic Resources.dhr.virginia.gov (opens in a new tab)
  6. Walker. 1999. Flint Run Jasper. Virginia Department of Historic Resources, Lithics (Projectile Points and Lithics guide).dhr.virginia.gov (opens in a new tab)

Named stones of this kind

Points made from this stone

All materials