Gao

There are few advantages to being old. But one of them Maybe that your collection can span a long period of time. One of the interesting things I have noticed is the fact that I can see in my specimen on occasion the changing state of the weathering of the fall. The photograph above is of three Gaos from my collection. I have probably thirty or so spanning thirty years. Some have been cleaned and others are as found. These three are as found. The one on the left is one I obtained many years ago. It is as jet black and beautiful as the day it fell because that is nearly when it was gotten. The one in the middle was purchased about ten years ago and is not nearly as smoothly black. The one on the right is one I purchased last year in Tucson. It has no black remaining. Though I know that I could return it to a much darker appearance if I was to powder blast it.

The old specimen on the left weighs 34.3 grams The middle specimen weighs 17.76 grams. The right hand meteorite weighs 24.86 grams. I have not reason to doubt that these are all Gaos though that fall has some interesting history surrounding it and it is now called Gao-Guenie. Specimens that appear as the one on the right can be made by powder blasting to look much like my meteorite on the left. Such cleaning will remove a thin outer layer of the weathering and the fine fusion crust detail. If you look at the specimen in the middle you will note that it still has significant detail in the fusion crust, but that the sharpness is gone and there is a general rounded and smoothed appearance to all the texture. There is little further deterioration seen between the middle and the right hand specimen. The only difference is a much increased amount of chemical alteration of the surface, producing the light brown color. The texture itself is not really changed.

Gao-Guenie
Fall March 5, 1960 17:00 hrs.
Burkino Faso

H5 Ordinary Chondrite