Axtell
Stone: Chondrite, Carbonaceous, Type: CV3.
Found: 1943, recognized: 1993.
McLennan County, Texas, USA.
Originally unearthed by a farmer plowing a field in 1943, it was not officially recognized as a meteorite until 1993. But what a meteorite: A rare Carbonaceous chondrite.
Carbonaceous chondrites consist of some of the most primitive material in the solar system. The round features in this slice are 'chondrules,' which formed as free-floating molten rock droplets in the early solar nebula, before they combined with dust and other particles to make these "primitive" meteorites, 4.54 billion years ago.
The white patches visible are 'calcium aluminum inclusions,' remnants of the supernova that resulted in the formation of our entire solar system (sun, planets, asteroids, comets...).
Photo courtesy of New England Meteoritical Services
This slice is part of our collection and weighs 7.8 g.
Here's a large, beautiful slice of Axtell.
Photo from the Arthur Ross Hall of Meteorites, American Museum of Natural History.
Credit: Taken by Christopher Ebel, a volunteer in the Department of Earth and Planetary Sciences, American Museum of Natural History. Copyright adheres to AMNH.
Note – from AMNH
Chondrites are considered "primitive" because the rock-forming elements in them are present in the same relative proportions as they are in the sun. In fact, if you could cool a piece of the sun so you could hold it in your hand, you would be holding a piece of carbonaceous chondrite, like Axtell.
A Few Words About the CV Group
The chondrites of this family are named after the Vigarano meteorite which fell in Italy in 1910. Scientists call the Vigarano meteorite a “type specimen,” in a sense setting the group standard that other meteorites must meet in order to be called a member.
The CV group has about 50 members, but the number of actual CV falls is lower since many of them are paired finds from the hot deserts of Africa and the blue-ice fields of Antarctica.
What's interesting about the group is the structure and composition of these carbonaceous chondrites is close to that of ordinary chondrites.
For example, in its dark-grey matrix of mainly iron-rich olivine, the CV meteorites exhibit large, well-defined chondrules. These droplets are made of magnesium-rich olivine, often surrounded by iron sulfide – which you can see in the above photo as the rust halo inside some of the chondrules.
The meteorites of this group also contain white, irregular inclusions of different sizes that often make up more than 5% of the meteorite. These inclusions are high-temperature minerals called CAIs (calcium-aluminum inclusions) and are composed of silicates and oxides of calcium, aluminum, and titanium.
And because of their early solar nebula history, these large CAIs have been intensely studied in the famous meteorite of Allende.
Side Trip - Allende
Allende fell in Mexico in 1969, shortly before Neil Armstrong took his first step on the Moon.
The CAIs of Allende contain fine-grained, microscopic diamonds - and those diamonds exhibited strange isotopic signatures that pointed to an origin outside of our solar system.
They were interstellar grains that proved to be older than the earth and the sun, and probably the product of a nearby supernova -- a dying star that made its last breath when our own system formed.
Traces of this supernova have been trapped within the CAIs and preserved in the CV group and other carbonaceous chondrites to this day.
Terms
As we have seen with other meteorites, Axtell is a beautiful chondrite. Here's some of the terms used to describe the meteorite.
Definition of Carbonaceous
- Adjective. Relating to or consisting of or yielding carbon.
Photo from the Wolf Research Group – Murchison Chondrite, 1969
http://carbon.indstate.edu/wolf/cosmochem.html
The average Carbonaceous Chondrite contains:
| Element |
% by Weight |
| ----------------------------------------- |
| Carbon |
2.0 |
| Metals |
1.8 |
| Nitrogen |
0.2 |
| Silicates |
83.0 |
| Water |
11.0 |
| ----------------------------------------- |
At most, they can be 20% water and can contain as much as 4% carbon. |
