Isheyevo

Right now Isheyevo is being called a CH/CBb and might not even be a chondrite in the usual sense of the term. It is a complex mix of components from different sources. For example, there are two distinct populations of CAIs. There are two sets of chondrule textures corresponding to two blended lithologies. And the phyllosilicates found as shells around some chondrules are compositionally different than those found in hydrated matrix lumps – of which there are three types.

David Weir’s excellent site presents a broad digest of recent work on this member of the CR clan. His Meteorite Studies site offers both overviews and extensive detail. It presents all credible sides when there are differing views and it is updated often.

http://www.meteoritestudies.com/protected_ISHEYEVO.HTM

http://www.meteoritestudies.com/

Isheyevo is dominated by a metal-rich lithology with 50% to 60% nickel-iron. Other parts have as little as 7% metal. The following pictures are of metal rich samples.

 

 Looking past the saw marks we see that even within the metal-rich lithology there are variations in silicate distribution. Here they appear in waves. This part slice is 25 mm tall. Isheyevo CH/CBb

 

 Thin section with light reflecting to highlight metal. Sample is 16 mm wide. Isheyevo CH/CBb

 

 Thin section with transmitted light. Sample is 16 mm wide. Isheyevo CH/CBb

 

 Center section of the same thin section in transmitted cross polarized light (XPL). Isheyevo CH/CBb

 

 Detail of the same thin section. The two largest chondrules appear to have layered forms. XPL. Isheyevo CH/CBb

 

The black sectors are metal grains surrounded by silicates. Incident light. Isheyevo CH/CBb

 

A large chondrule surrounded by metal – the light colored material – and containing metal internally. Incident light. Isheyevo CH/CBb

 

Variety of features. XPL. Isheyevo CH/CBb

 

Variety of features. XPL. Isheyevo CH/CBb

 

Variety of features. XPL. Isheyevo CH/CBb

 

Variety of features. XPL. Isheyevo CH/CBb

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About the Author

John Kashuba
John is a natural history enthusiast living in Oregon.
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