Another Unclassified NWA
One of the few unclassified meteorites I got in Tucson this year needed just a little lapping to make a large window. So it was off to the garage and the diamond lap. There is nothing really special about this stone. It was a nice size and had an interesting shape and the price was really great so what's one more among hundreds I already have. I know that this one has been around for a long time from looking at the outside. It is well cracked and its fusion crust is gone. Yet, when I lapped it I was surprised to find it had a good amount of its metal still. There are some chondrules visible when it is turned in the light just right, though the matrix is too dark to make photographing them possible. They are well defined so a type 4 is a good guess. Though type 5 would probably be just as good a guess whithout having a thin section to look at. From the amount of hematite that I can see it had quite a bit more metal originally. Certainly an H by just looking would be another OK guess. But, as much as it is weathered it is still a lot better preserved than many others I have cut that are in far nicer shape on the outside. There really is no way to guess from the outside of an old meteorite how the preservation of the inside will be.
The stone weighed 122.5 grams before I put it on the lap. After lapping and polishing it weighs 118.0 grams. Not as much as I would have lost in a cut and the result is still nice. I doubt that getting in deeper would reveal a nicer condition on this stone. As can be seen in the next photograph it has cracks on the sides which have allowed water to penetrate the meteorite at many places. I would guess that it is altered fairly uniform throughout. You can also see the high polish on the lapped face in the next picture.
I'm hear these lonely meteorites crying out as I walk by rooms at Tucson. It is just hard for me to not give them a good home. Sometimes they have to give up a part of themselves to make me happy though. But, after the brief pain of have some grinding done they are left alone to be admired for years to come. This one only required about 5 minutes to prepare. Lapped with 99% isopropyl alcohol and polished on impregnated plastic polishing film it is a fast and easy task to improve a broken stone.