Archive for the ‘Tektites’ Category

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Storing (and transporting) my meteorite collection

October 18, 2020

I finally got around to organizing my (small) meteorite collection. I don’t have the space for a display cabinet right now, and when the pandemic lifts I’d like to be able to easily transport everything to schools and club outreach events, so I got a couple of HDX storage cases from the toolbox section at Home Depardieu. I think these things are the bee’s knees. They’re big, sturdy, and dirt cheap–right now you can get two cases, which lock together with the side tabs, for ten bucks. Best deal going. I got a couple of sets for Vicki, to help organize her histology slides, and they’re working great for her, too. I’m tempted to buy a bunch of them just to have them on hand in case they ever stop making them or jack up the price.

I cut bubble wrap to fit and taped it into the lids, padded the little cubbies, put cards at the back of each cubby with info on each specimen, and every time I get silicone gel packets with anything I toss them in the front of the case.

I did the same for my impactites. At the meteorite show-and-tell at a PVAA general meeting a couple of years ago (described here), the sight of Ken Elchert’s monster tektite really fired my interest, and I went on a little tektite-collecting binge. 

Here are my indochinites, from an impact in Southeast Asia, about 780,000 years ago, that produced the Australasian strewn field (australites, indochinites, philippinites, rizalites).

And here are the rest. The philippinite is from the same impact as the indochinites, it just flew further. The australites flew the farthest of all, and as they re-entered Earth’s atmosphere (yeah!) their front edges melted and flowed to produce perfect little aerodynamic heat-shield shapes called ‘buttons’. Real ones are a little outta my price range right now, but I got a nice cast of one from Gary Fujihara on eBay (here’s his store). The bediasite is a personal favorite–it’s from the impact 35 million years ago that gouged out Chesapeake Bay. That tektite was sitting in east Texas for more than half of the Age of Mammals before someone recognized it and collected it.

Why am I so fascinated by tektites, in particular? I think it is the diversity of shapes. Tektites are travelers in space and time, a frozen snapshot from the moment that a giant rock from space slammed into our planet. Each one is unique, and its shape tells a story about its flight through the atmosphere and subsequent erosion. Tektites embody everything that interests me: space, time, astronomy, geology, aerodynamics, and the history of our planet.

Not a tektite: a 31g piece of nickel-iron shrapnel from the Sikhote-Alin airburst in 1947. See this post for more details, and photos of a bigger piece.

Parting shot: I have a question about storage. Right now I’m just using cotton balls for padding in my cases, because they were fast and cheap. Are there any downsides to using cotton balls over the long run? Should I spring for some Polyfil, or other artificial fiber? I live in a fairly dry climate and mold and mildew are generally not problems. Thanks in advance for any wisdom!

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My meteorites: moldavite (2g)

October 4, 2018

I didn’t even know moldavites existed until last year. One of the highlights of my trip to the 3RF Messier Marathon in the spring of 2017 was seeing Jeff Barton’s meteorite collection. He set it out for us to peruse one day, and it covered a classroom’s worth of tables. I barely knew from meteorites back then–hadn’t caught the bug yet–but a few things stuck in my head. One was his collection of Chelyabinsk meteorites from the 2013 airburst. Another was his collection of tektites. I knew what tektites were in general, but I’d never seen any firsthand. Jeff had a really nice, good-sized moldavite and he encouraged us to hold it up to the light so we could see that it was translucent glass. I got a few snaps of that and I definitely remembered it.

A couple of months later I was driving back from a museum visit in Mesa, Arizona, with a colleague, and we stopped for lunch and gas. There was a rock shop across the street so I thought, “What the heck” and went in. Amongst the other treasures was this little moldavite in a little display case. I checked it out carefully–there is a burgeoning market for fake moldavites, but most are easy to spot as cast glass. All signs point to it being genuine, so I bought it as a souvenir of the trip.

Fifteen million years ago, a massive impact in what is now southern Germany created the Nördlinger Ries crater, which is 24 km (15 miles) across and still up to 150 meters (~500 ft) deep, despite considerable subsequent erosion. The impact scattered showered tektites over a vast area of east-central Europe, including parts of southern Germany, Austria, and the Czech Republic. Moldavites are typically green. They draw their name from the Moldau River in the Czech Republic, where the first pieces to be scientifically described were found.

This moldavite is one of my favorite pieces in my little collection. At outreach events I encourage people to hold it up to the light, and it never fails to impress. It’s strange, but satisfying, to hold a piece of glass 15 million years old.

Before I started reading up on meteorites earlier this year, I assumed that tektites must be pretty common, since they are impact glass from big meteorite impacts, and the Earth has had hundreds or thousands of crater-forming impacts in the last few hundred million years. But most known tektites can be traced to just four impacts:

  • an impact near southeast Asia or Australia, about 780,000 years ago, that produced the Australasian strewnfield (australites, indochinites, philippinites, rizalites);
  • the Lake Bosumtwi impact in Ghana, about 1 million years ago, that produced the Ivory Coast strewnfield (ivorites);
  • the Nördlinger Ries impact in Germany, about 15 million years ago, that produced the Central European strewnfield (moldavites);
  • the Chesapeake Bay impact on the east coast of North America, about 34 million years ago, that produced a North American strewnfield (bediasites, georgiaites).

There are exceptions:

  • a Central American strewnfield in Belize, with tektites dated to 820,000 years ago, which only started to be reported in the 2010s;
  • Darwin glass, an impact glass associated with the Darwin Crater near the west coast of Tasmania, estimated to be about 810,000 years old;
  • Libyan desert glass from the eastern Sahara, inferred to be the result of an impact or airburst about 26 million years ago (strictly speaking, probably a surface melt rather than melted material thrown through the air).

If you know of a tektite strewnfield or impact glass site that I’ve missed, please let me know in the comments.