Crater Glass or Tektites?
It is very unlikely that I will ever have the opportunity to travel to the Zhamanshin Crater. Which is a shame since it is among the top most interesting impact craters for me. The variety of impact related rocks and glasses from Zhamanshin is remarkable. At the last Tucson show I took a great deal of time sorting out some particularly fine irghizites which originate from Zhamanshin.
I remember many conversations with Darryl Futrell about Zhamanshin glass and irghizites. As was always the case he had some interesting ideas of his own about them. For instance he thought that some of the glass material from Zhamanshin was remelted tektite glass, and that the impacting body that formed the crater was a gigantic piece of Rhyolite that contains tektites as part of its make up. I think that the presence of small glass specimens similar to irghizites at many craters says that they form in the impact and are not something that came with the impactor. But, regardless of all that irghizites have held my interest for many years. I have some large ones in my collection, but there is just something about the tiny ones I really love. So I offer for your viewing enjoyment this month a nice assortment of irghizites. They come in many of the forms that tektites also occur in. Teardrops, spheres, oval forms, and rods, are common shapes, however because the glass appears to have not travels very far at all into the air other forms occur. Some of these are intricately branched and bridges shapes with multiple projections or threads. And like Wabar glass and Henbury glass many of the irghizites have surfaces that are covered in tiny bumps. Which appear to be even smaller droplets of glass which attached themselves to the larger ones while still in a plastic state. The basic facts about the crater are listed below.
Kazakhstan N 48° 20' E 60° 58'
Age: 900,000 ± 100,000 years
Diameter 13.5 kilometers, exposed at surface
I enjoy weighing very small objects on precision scales. I have for on this occasion only recorded on the photos the weight to about one ten thousandth of a gram. For some I did have more accurate weights. They will probably never be weighed again or ever sold by weight, but it is always fun for me to do the weighing.