A few of us were talking meteorites when one friend mentioned Moorabie. When I couldn’t recall the stone I was admonished to refresh my memory as soon as possible. I make amends with this column. Even before checking my small collection I consulted David Weir’s Moorabie page to see what the score was. He lays out the reasons for the
D’Orbigny The D’Orbigny angrite is famous for a lot of things. Among them are holes – vugs and vacuoles. The irregular vugs are usually filled with a tangle of well formed dark augite crystals. The vacuoles or vesicles are spherical. Most are empty. Some contain glass. These three dimensional features are hard to appreciate in two dimensional pictures. Trying to
Not all CV3 carbonaceous chondrites are alike. More than most, NWA 6207 makes it easy for us to see that its components went through a succession of processes before they were delivered to us. Existing large mineral grains were incorporated into chondrules. Chondrules formed, solidified and then were included in subsequent chondrules. Mineral grains evolved, chondrules gained layers and their
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
For a long time Begaa had no official name and several stated classifications. Now Begaa is a synonym for NWA 4910 LL3.1. Whether this change is welcome, a comedown or something else is a matter of opinion. But we can agree that it is one fine meteorite. It’s a rock you can show any novice and say “THIS is a
The Meteoritical Bulletin database lists NWA 1109 as a polymict eucrite – at least a 2.54 kilogram portion of the find was classified that way. I know that in 2002 and 2003 some material was sold as NWA 1109 howardite. For some of the discussion of Eucrite versus Howardite you can Google NWA 1109 howardite. There are more than 20
Greg Hupé tells about his new ungrouped achondrite in this issue of Meteorite-Times so this is a good time to show close up pictures of it. Dr. Tony Irving did the classification and we learned about this stone from his Meteoritical Bulletin writeup, an abstract and phone conversations. NWA 6704 and, evidently, at least one pairing are from a previously
NWA 5426 is a Rumuruti type chondrite. Most R chondrites show brecciation, though Rumuruti itself does not. They have a somewhat high ratio of matrix to chondrules and very little metallic nickel-iron. Chondrules tend not to be the fully melted types (barred, radial, cryptocrystalline and glassy) but, as you’ll see below, there are exceptions. Here are close-ups of a slice
Talbachat n’aït Isfoul is an eight kilogram meteorite found in Morocco twelve years ago this month. The Meteoritical Bulletin database lists it as an LL3. You’ll see it called an LL3.7, too. Sometimes it’s called Tagounite 019. As expected with those classifications it has largish, well preserved chondrules. With a ‘scope we find a variety of things.
The canonical thickness for thin sections is 0.03mm. Professionals depend on it. Collectors insist on it. Still, if we have to rely on a conventional light microscope there are some times when thinner sections show more features. The dark, fine grained matrix of low petrographic type carbonaceous chondrites can hide smaller mineral grains. Polish off some of that material and
Chondrules were molten droplets. What caused the melting is hotly debated (har). Chondrule textures reflect the extent of melting and rates of cooling. Porphyritic chondrules did not fully melt. Fine-grained porphyritic chondrules began cooling with many fine widely distributed unmelted mineral crystals. Coarse-grained porphyritic chondrules had fewer. Either type can contain larger grains that survived the melting episode and retain
Dar al Gani 1040 is an odd CV3. It has a light colored matrix and light colored chondrules. In the hand a fresh slice sparkles with metal in the chondrules and the chondrules stand proud of the matrix. It seems the matrix is friable and sheds a little during cutting. In thin section it is rich with features.
Steve Arnold looked like he was passing appetizers. He was circulating with a tray of gem jars in Tucson. Each one held a cm size morsel of Vaca Muerta olivine. Mesosiderites aren’t known to be olivine rich so these were pretty cool. Yes, please, may I have two? Vaca Muerta olivine appears to be from the mantel of the mesosiderite
I don’t think CK meteorites are much to look at except those rare slices with huge, gnarly CAI. You pretty much get dark chondrules in dark matrix. I have one fairly dense slice that someone polished which made features essentially disappear. Thankfully that wasn’t done to this slice.
It’s worth a few minutes to peruse a howardite just for the textures – viewing it in hand or with a loupe or ‘scope like we do here. Howardites are the compacted soil of the asteroid Vesta. They are a mixture of fragmented rock that has been excavated – from both shallow and deep – mixed and lithified by impacts.
