A Eucrite with Chondrules

Northwest Africa 10674 was purchased by Marc Jost as four pieces totaling 1,193 grams. It was classified by Irving and Kuehner as a polymict eucrite with a significant portion of metal-bearing H6 chondrite clasts with other asteroid debris.

This 66 gram slice is 80mm long. In general, the dark clasts contain metal and are chondritic, the light clasts are eucritic. Marc Jost photo.

The slice is about a centimeter thick so only large clasts show on both sides. Marc Jost photo.

We had seven thin sections made from a separate 8 gram part slice. Note the metal reflecting from within the dark chondritic clasts. Minor nickel-free metal was found but the vast majority of metal is nickel bearing kamacite from one or more chondrites.

In transmitted light this closer view of the above thin section shows staining from metal and troilite.

Center section of the above thin section in both reflected and transmitted light.

Portion near the top of the same thin section in both reflected and transmitted light. Note the radial pyroxene chondrule in the dark clast in the center.

Radial pyroxene chondrule in clast in NWA 10674 polymict eucrite. Plane polarized light, PPL.

Radial pyroxene chondrule in clast in NWA 10674 polymict eucrite. Cross-polarized light, XPL.

The other thin section has an altered radial pyroxene chondrule embedded near the edge of this large dark clast.

Altered chondrule about 0.4mm in diameter embedded near the edge of a large dark clast. PPL.

When polarizing filters are rotated the shadow of optical extinction progresses around the fanned laths assuring us that this is a radial chondrule. XPL.

An oval object in a different thin section. Maybe a chondrule, maybe not. XPL.

Another suspicious object. XPL.

And another. PPL.

XPL.

These bright spots, like many others, appear to be intergrown metal and troilite, magnified below in reflected light.

John Kashuba

John is a natural history enthusiast living in Oregon.