Meteorite Monday: Ordinary Chondrites

Before I move too far into this post I should define two important terms so that we’re all on the same page:

  • Chondrite- basically the sedimentary rock of the solar system. It’s an aggregate of the left over material from the formation of the solar system.
  • Chondrule- Kind of the vagabonds of the proto solar system. They started off as molten spheres of either pyroxene, olivine or another silicate mineral that glommed onto the nearest asteroid, cooled and became the round features so prominent in ordinary chondrites.

If you have further questions (or even corrections/critiques) post it in the comments and I’ll do my best to address it.

The term “ordinary chondrite” is a bit misleading. Rocks that formed during or even before the formation of the solar system are anything but ordinary. Rather, they are the most commonly found meteorite on the earth. Their stony composition makes them more resilient than their carbonaceous brethren and as such, there is a ton of material about them that one can study. I don’t want to get into the details in this post because I need a little more time to study it and do the topic justice. However, I will list the three classes of ordinary chondrites (from Wikipedia):

  1. H Chondrites- Highest total iron, high metal, but lower iron oxide in the silicates
  2. L Chondrites- Lower iron total AND metal content, but higher iron oxide in the silicates
  3. LL Chondrites- Low iron total and low metal content, but higher yet in iron oxides

So basically, what separates the three classes is the iron and iron oxide content. As one goes up the other goes down.


Ordinary Chondrite Northwest Africa 1756

Ordinary Chondrite Northwest Africa 1756- image from Northern Arizona University

Those round blobs in this image are the chondrules. In a later post I’ll give more information about this particular chondrite.