METEORITE OR METEORWRONG?

concretions

Hematite and magnetite are two iron oxide minerals and most iron ore deposits consist mainly of hematite, magnetite, or both.

Hematite concretions or nodules, sometimes called ironstone concretions, are often mistaken for meteorites because their unusual shapes catch people's attention and they are denser than most other rocks.
Hematite concretions are formed in sedimentary rocks by oxidation of pyrite (iron sulfide) crystals or precipitation of iron oxide from iron rich solutions. Concretions, which may also be composed in part of the iron oxy-hydroxides, limonite and goethite, come in a wide variety of bizarre shapes. Sometimes they're shiny on the surface, which might give the impression of a meteorite fusion crust. Note that while a hematite concretion is rich in iron, it is usually not particularly magnetic. Magnetite, on the other hand, is highly magnetic, and it often forms nodules, too.

Clicking on some of the smaller images below will bring up enlargements.

 

Below are some solid hematite concretions found near Wentzville, Missouri. Thanks to Joel for the photos.



Below are some more hematite concretions from the country of Georgia. Thanks to Besik for the photos.



Here are some from China. Thanks to Julia for the photos.


Here are some more from the U.S. Thanks to Cary for the photos.


Here are good ones from Isabelle, who found hers in Australia (left), and Jean, who found hers in Massachusetts (right).


Thanks to Micah, here are two views of another one from Missouri.


Thanks to Theresa for two views of a concretion from Texas.


I found two envelopes in my mailbox one day. One, from Texas, had the stones on the left. The other, from Wyoming, contained the stone on the right. All are hematite concretions. Thanks Frank and Joe.


Thanks to Warwick from Australia for these two.


Thanks to Ben for these two views of a hematite concretion


A most excellent specimen of what I call a dog-turd concretion. Thanks to Mason in Texas.


Thanks to Ron from Missouri for these two holey hematite concretions.


Thanks to Christine for this one.

Thanks to Adam for this fine specimen.

Thanks to Toby for this one from the Sahara.
 
  

This one's from Steve in Portland.


Tim said this one is from Wisconsin.


And Paul said this one is from Pennsylvania.


Jarvis sent this photo of hematite concretions from west Texas.


These two are from Peru


Thanks to Mark for this one.
  

Here's a likely candidate, from Peru! It resembles meteorwrong no. 194. Thanks Jon.

  
Sometimes hematite makes coatings on other rocks. Thanks to Scott for this one.


Here are two other examples hematite coatings. Thanks Tom and Søren.


Here are two other examples hematite coatings. Thanks Tom and Søren.



  
I was given the stones below as a child by my grandmother. I don't know where she got them, but she was from New York state. She called them "Indian paint pots." (See, for example, Garvies Point concretions). The stones are hematite concretions used by native Americans to paint their faces. The blunt end of the stone in the upper left could be rubbed in the bowl of another stone with water (we used saliva as kids, of course). A reddish paste was produced because hematite concretions are not particularly hard (which is why they make a red streak in the streak test, below). Because of their high density, large hematite concretions have been used since prehistoric times for tools (see Lithic Casting Lab).




Some of the rocks in our Photo Gallery of Meteorwrongs are also hematite concretions:

024 | 046 | 055 | 152 | 155 | 170 | 174 | 186 | 189 | 194 | 205 | 241 | 277

See some "cannon ball" concretions


Hematite is easy to identify because it makes a red streak. Also, hematite concretions are denser (heavier for their size) that any kind of stony meteorite or most other kinds of earth rocks. For example, the specific gravity of an ordinary chondrite (the most common kind of meteorite) is about 3.9 whereas the specific gravity of a hematite concretion is 4.2-5. For a good discussion of how to measure specific gravity, click here.

Below are some websites that discuss how concretions form and that have photos of concretions:


www.catchafallingstar.com
www.catchafallingstar.com


Prepared by:

Randy L. Korotev


Department of Earth and Planetary Sciences
Washington University in St. Louis


Please don't contact me about the meteorite you think you’ve found until you read this and this.

e-mailkorotev@wustl.edu