Identify if a Meteorite? Fusion Crust, Magnetic, Olivine

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Discussion Overview

The discussion revolves around identifying a rock that may or may not be a meteorite. Participants examine characteristics such as fusion crust, magnetic properties, metal flakes, and the presence of olivine crystals. The conversation includes both observational claims and requests for photographic evidence to support identification.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants assert that the rock has fusion crust, is magnetic, contains metal flakes, and features orange olivine crystals.
  • Others challenge the identification of the crust as a fusion crust, questioning how it can be determined as such without further evidence.
  • Several participants emphasize the need for a photograph to assist in the identification process, noting that without visual evidence, it is difficult to provide accurate feedback.
  • One participant suggests that the rock may actually be a meteor that burned up in the atmosphere rather than a meteorite.
  • Another participant states that the rock resembles Earth rocks, specifically suggesting it could be greywacke, and claims there are no observable signs typical of meteorites.
  • Some participants express skepticism about the presence of olivine and metal flakes, indicating that these features are not clearly visible in the provided descriptions.
  • There are claims that many Earth rocks can also be magnetic, complicating the identification process.
  • One participant mentions that the rock may have developed a weathering crust rather than a meteoritic fusion crust.

Areas of Agreement / Disagreement

The discussion remains unresolved, with multiple competing views on whether the rock is a meteorite or an Earth rock. Participants express differing opinions on the characteristics of the rock and the validity of the claims made about it.

Contextual Notes

Participants note limitations in the identification process due to the absence of a photograph and the quality of the camera used to capture images of the rock. There are also unresolved questions about the specific location where the rock was found, which could influence its classification.

  • #31
Het Patel -
Like the others, overall it does not strike one as meteoric origin.
Looks more like a dense basalt that's been river tumbled into the shape it now has.
Basalt can be magnetic since it's rich in iron.
It can also have olivine crystals which colors can vary.
A local university with a decent geology department should be able to thin section it and put it on a petrographic microscope which will definitively answer the question.
 
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  • #32
Baluncore said:
When the hot meteorite slows down and begins to cool in the lower atmosphere, the surface shrinks first, opening cooling cracks in the surface. Then the inside cools and shrinks which partly closes the surface cracks.
Actually, I will clarify that comment. I should have done so when I first read it.
Not all stone meteorites end up with a cracked fusion crust. Some are, most are not. See the examples I posted from my collection
near the start of the thread.

Contraction cracking is caused the strong cooling high in the atmosphere, 15 - 20 km or so. This can be as it passes through particularly
cool layers of the atmosphere. A fellow collector who does indepth meteorite studies commented that frost can form on the fusion crust
causing the cracks and in extreme cases a layer of ice can form, making those cracks even more pronounced.

Surprisingly, the inside of the meteoroid doesn't heat up overly much. Rock is a very good heat insulator.

My favourite cracked crust meteorite's is Ghadamis from NW Africa, Algeria, from memory.
This is a 1.45kg sample.

Brett Joseph 1.45kg Ghadamis2.jpg
 

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