Metal in Ordinary Chondrites

Most (~85%) stony meteorites are ordinary chondrites. Below are some photos of sawn faces of ordinary chondrites. The brightest materials in each photo are metal grains (veins in “Richarton”). Ordinary chondrites contain iron-nickel metal and, consequently, will attract even a cheap magnet.

Labeled as “Richarton, ILL.” but probably Richardton H5 (North Dakota, fall, 1918). In the closeup on the bottom, saw marks are visible in the metal vein. Notice that the metal grains are typically less than 1 millimeter in size. Photo credit: Randy Korotev

Allegan H5 (Michigan, fall, 1899). Photo credit: Randy Korotev

Mocs L6 (Romania, fall, 1882). In the closeup on the right, saw marks are visible in the metal grains. Photo credit: Randy Korotev

Bjurböle L/LL4 (Finland, fall, 1899). The circular things are chondrules. Photo credit: Randy Korotev

Two views of a sawn slice of Independence L6 (Missouri, fall, 1917), with electronic flash lighting (top, with millimeter ticks on scale) and natural sunlight (bottom). Thanks to Karl Aston for the sample. Photo credit: Randy Korotev

Two views of a sawn slice of Cape Girardeau H6 (Missouri, fall, 1846), with electronic flash lighting from two different angles. Thanks to Karl Aston for the sample. Photo credit: Randy Korotev

Unnamed Northwest Africa (NWA) chondrite. Photo credit: Randy Korotev

An unnamed, probably LL, chondrite from the US. Sawn face on top, exterior with fusion crust on bottom. Thanks to Karl Aston for the sample. Photo credit: Randy Korotev

A large slice of Seminole (f) (H5) . There are thousands of sub-millimeter metal grains in this slice. Thanks to Phil Mani for the sample. Photo credit: Randy Korotev

Two faces of a saw cut through slice of Harper Dry Lake 036 (L6). Note the melt vein running through the center. Millimeter ticks on left. Photo credit: Randy Korotev

Chondrules and metal grains on a sawn face of an unnamed chondrite (probably H5) from northern Chile. Millimeter scale in background. Photo credit: Randy Korotev

Ordinary chondrite pebbles found in the Sahara desert. Most are broken, but a partial fusion crust is intact on many of them. Notice that despite that all of them contain metal, they are not rusty colored. Photo credit: Randy Korotev

Two views of the same stone, another unnamed ordinary chondrite (probably H chondrite) from northwest Africa. Top: The unspectacular weathered exterior in direct sunlight. Bottom: A polished, sawn face in direct sunlight. All the dark areas are alteration rims (rust) around the metal grains. It is likely that this meteorite fell thousands of years ago. Photo credit: Randy Korotev

This meteorite violates a number of the recognition principles that I stress in “Some Meteorite Realities.” There is no obvious fusion crust. The surface is not glassy or shiny; there are no regmaglypts. The exterior has some ridges and one point. It’s clearly a broken fragment of a larger meteorite. If you look closely at the upper image, however, there are shiny metal grains along all the protuberances (points, ridges) because these areas have been abraded from handling. Also, the specific gravity is 3.42, well within the range of ordinary chondrites.

This is one of many fragments of ordinary chondrite from Algeria known as Northwest Africa 869 (L3–6, 2 tons). On the top, the fusion crust is still intact. Notice that it is smooth with no holes. The rougher portion on the bottom of the photo is where the fusion crust as broken off after it fell. This meteorite probably also fell thousands of years ago and has been exposed to harsh conditions in the desert. Note that there is no obvious metal. L chondrites do not contain as much metal as H chondrites. The rock does attract a magnet, however.

Two views of an unclassified ordinary chondrite fragment from the Sahara desert. Top: The fusion crust is dark and smooth. If this were a fresh fall, it would be shinier. In most meteorites the fusion crust is darker than the interior. Bottom: Rusting of the metal grains has led to reddish staining on the weathered, broken face of the meteorite (electronic flash lighting).