THE YAFA H5 ORDINARY CHONDRITE
A METEORITE FALL IN YEMEN, 2000

Part II, Higher-Resolution Images


Opaque minerals, chondrules and fusion crust.


The thin section [63 kb]

The Yafa chondrite was classified using this polished thin section, an area of 27x12 mm. It is easy to see a few of the better-defined chondrules, scattered opaque phases (Ni-Fe alloys and FeS) and a few mm of the thin fusion crust at the lower right. The section is part of the type specimen, which includes 93 g of material with attached fusion crust.



Opaque minerals [73 kb]
1. Metal phases in the Yafa chondrite are dominated by kamacite (white, highly reflective Ni-Fe alloy with 6-7 weight percent Ni) plus troilite (yellowish FeS, seen in the corner of this view). The Ni-rich phase tetrataenite (NiFe) is visible as a small, highly-reflective cream-coloured grain on one extremity of the main kamacite mass (upper left quadrant of photo). A small grain of grey chromite is visible in the silicate groundmass, near the edge of the kamacite. Photomicrograph, 80X magnification, long-axis field of view 1.4 mm, viewed in plane-polarized reflected light.



Metal-rimmed chondrule [85 kb]
2. Metallic rim on large chondrule. A large pyroxene-rich chondrule displays a partial rim of Ni-Fe alloys (mainly kamacite) plus lesser troilite. Photomicrograph, 40X magnification, long-axis field of view 2.8 mm, viewed in plane-polarized reflected light.






Small chondrule [106 kb]
3. Granular olivine chondrule. This small, perfectly circular section through a chondrule shows that it is composed largely of fine granular olivine. In reflected light it is clear that the chondrule also contains roughly 10 volume percent glass and 1 percent kamacite, interstitial to the olivine. Well-formed, intact chondrules which are clearly differentiated from the groundmass are not common in this H5 chondrite. Photomicrograph, 160X magnification, long-axis field of view 0.7 mm, viewed in cross-polarized transmitted light.



Fusion crust [85 kb]
4. A profile through the outer surface of the Yafa chondrite displays the glassy, bubbly, metal-free fusion crust some 0.3 mm thick, and an inner layer in which the troilite is partially remobilized into impersistent, hairline fractures. Less than 1 mm inside the stone, the typical textures of the chondrite can be seen, with assemblages of fine and coarse-grained metal, sulphide and silicate phases. Photomicrograph, 80X magnification, long-axis field of view 1.4 mm, viewed in plane-polarized reflected light.




Document last revised 31 October 2001.

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