09 August 2013

Beautiful Fukang meteorite

The Fukang meteorite is a meteorite that was found in the mountains near Fukang, China in 2000. It is a pallasite—a type of stony–iron meteorite with striking olivine crystals.
This information from the Reddit discussion thread:
The pattern, called a Widmanstätten pattern, is due to what is called subsolidus exsolution. Iron meteorites will crystallize as a mineral called taenite. Once the mass is cooled and if it is cooled slowly enough, kamacite and taenite will form. The cool thing to realize is that this is done very slowly and all while solid! No melting is taking place... Meteorites just have stupidly slow cool down rates since the vacuum of space make an awesome insulator.
Photo from imgur, where the title pun is repeated ad nauseum (but it serves as a good way to remember the identity of the material).


  1. I have a slice of the Esquel pallasite- this one is much more beautiful!

  2. I've recently come across pallasites while doing some research on olivine in asteroids and meteors.

    Probably more than you want to know:

    Based on my research, I wouldn't necessarily agree with the statement about meteoroids/asteroids cooling down so slowly. First of all, the Reddit writer doesn't even know that meteorites do not exist in space. They only become meteorites upon landing on Earth. Meteors" are ones flaring up as they enter the atmosphere. After that they become meteorites if they survive the atmosphere - which most do not do. BEFORE they enter the atmosphere, they are called "meteoroids", which essentially means small asteroids. In space there are basically only comets and asteroids.

    Also, even a quick read in Wikipedia will show that pallasites are understood to have been created WITHIN asteroids, and a particular KIND of asteroid at that - a differentiated asteroid. "Differentiated" means separated into a crust-mantle-core layering. NONE of the asteroids known has been shown to even HAVE a mantle or a core, though Vesta, the 2nd largest, has been interpreted as having a mantle. However, the Dawn mission that visited both Vesta and Ceres (the largest asteroid), failed to discover any direct evidence of a mantle. It had been thought that the large Rheasilvia crater at Vesta's south pole would show olivine - proof of a mantle - but, alas, even though it was 80-100 km deep in a body only 475-550 km across, everyone was very surprised that no mantle material had been dredged up by Rhealsilvia's impactor.

    Pallasites? Olivine is THE material of most of Earth's mantle, beginning n the lower part of the lithosphere - the aesthenosphere - and going all the way to the edge of the outer core. The core is made up mostly of iron, as we all know. At the core-mantle boundary, it is not an immediate change from olivine to iron. The two are thought to gradually phase from one to the other. THIS is the region from which pallasites are born. it is REALLY, REALLY deep within the Earth. It takes a lot of gravity AND a lot of depth to provide the pressure and 2200°C temperatures to form olivine.

    No olivine formed out in space. The pressure is so vastly inadequate that it is simply impossible. The person who wrote that IMHO didn't know what they were talking about. Someone made all of that up. The pallasites came from dep within a differentiated planet or large moon. How it got OUT, that is a question still to be answered. Some astronomers speculate that all of the impacts over the last 4.6 billion years may have stripped the crust and core off of a differentiated body, leaving only the core, but strewing the rest out into space - to become asteroids of varying sizes.

    But there is a problem with that, too. Based on our understanding of the Earth, it is thought that mantle material makes up about 75% of all the mass of a differentiated planet or planetoid. That leads to the expectation that there should be a LOT of olivine out there and here, in meteorites found on Earth. The problem is that the olivine is not showing up very much. Only about 1% or less of meteorites have olivine in them. This is called "the missing olivine problem". And it is a biggie.

    I got into this research because of the Allende meteorite, which DOES have olivine - mantle material. My reaction was "WHAAAAAT?????!!! How can there BE olivine in a meteor?! It's made in the interior of planets, and it can NOT be made out in space."

    As to the slow cooling in space? This person who wrote this seems to think that conduction and convection are the main ways things cool down. He seems to not be aware that MUCH heat is given up in radiation, principally in the infrared. And such radiation, being EM, of course, happens in space. If EM didn't radiate, we couldn't even SEE stars and planets in space.

    Google "pallasite" and then look at all the images. Almost all of them are as beautiful as this one.


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