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meteorite
I was lucky enough to do a couple of art technician jobs alongside the incredibly generous Graham Ensor. Like most techs, he's an artist as well, but he's also an important meteorite collector. During breaks he would bring in different samples and discuss their origins, the different features that can be observed from their surface and the stories that went along with each of them. Graham gave me a small piece of meteorite Northwest Africa 869.
"Chondrites are named for their most prominent feature - millimeter-sized spherical bodies called chondrules. These chondrules (from the Greek for small sphere) formed 4.5 billion years ago in the Solar Nebula - the cloud of gas and dust from which the Sun, planets, asteroids, and comets formed. Chondrules are not found in terrestrial rocks. These chondrules, along with small mineral grains, accreted to form asteroids during the birth of the Solar System. Chondrites are, by far, the most abundant type of stony meteorite." - NASA.
Information about different meteorites is collected online at various places. The table below is pulled from The Meteorological Society website. The full listing for NWA 869 is here.
| Physical characteristics: | Most samples are individual meteorites but some fragments (mostly >1 kg) also occur. In most cases the fusion crust has been polished or ablated by wind erosion. Many samples are more severely affected and show faces with deep wind erosion features. Fracture faces, formed by ground collision, show a typical gray-green color and sometimes visible brecciation (light and/or dark clasts). Due to the coarseness of this breccia, there are some stones that consist of only a single lithology. |
| Petrography: | This chondritic breccia consists of about 75 vol% matrix with unequilibrated and equilibrated L-chondrite clasts (up to 5.5 cm), some of which display shock-darkening. Impact melt-rock clasts, themselves either clast-free or clast-poor, also occur and are strongly depleted in Fe,Ni metal and sulfide. | Geochemistry: | Northwest Africa 869 is a regolith breccia, containing solar noble gases and preirradiated lithologies. Olivine in lithic clasts: Fa0.2-49.2; olivine in matrix: Fa10.3-29.3; low-Ca pyroxene in lithic clasts: Fs2.1-35.9; low-Ca pyroxene in matrix: Fs7.0-23.9. Bulk oxygen isotopes: δ17O = 3.52; δ18O = 4.67; Δ17O = 1.09 per mil. Terrestrial age: 4.4 ± 0.7 ka. Preatmospheric meteoroid size and mass: 225 ± 25 cm, 120-230 T. |
| Classification: | Because NWA 869 contains unequilibrated clasts, its classification is revised to L3-6. |
I'll link a photo of my piece of NWA 869 below. It's cool to the touch and feels heavy. One side is a smoothed irregular dome. This is the fusion crust. This part is formed as the rock enters the earths atmosphere and the surface melts in the extreme heat. It solidifies to a smooth dark glass. This surface has been weathered in the desert and cracked in a leathery pattern. The other side is flatter and has a kind of mottled roughness.
| type | url | description |
|---|---|---|
| image | rnwa869-dithered.png | dithered image of NWA 869 piece. |
| image | nwa869-fusioncrust-dithered.png | dithered image of fusion crust side of NWA 869 piece. |
categories: text
~gg 02/23
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