The Twodot Chondrite: Montana’s Only Stone Meteorite

Twodot meteorite

This is the largest slice of the Twodot meteorite in terms of surface area. None can be larger since this slice came from the middle of the curved stone. The lightly brecciated and shocklined face is only outdone by the obvious orientation.

About two months before the end of last century, an hunter scouting a heard of elk literally crawled up on a meteorite. How did he know it was a meteorite and not one of the other billions of rocks lying around? Well, he just did. He believed it was from space even though the finder had never seen a meteorite before.

Twodot meteorite

The graceful curved leading edge of this slice shows the classic form caused by a stable run through our atmosphere.

No, the Twodot stone wasn’t smoking away while it melted the snow, nor was it a sphere full of holes like in the comic books. It wasn’t glowing green. And no it didn’t look like a freshly minted rock delivered recently to this planet. Instead it was just a rusty 47-pound stone with hints of orientation even to the untrained eye. No fresh crust on this weathering grade 3 rock. But there were enough characteristics that the finder retrieved the stone and kept it safe for years before someone in the know got a first-hand look. And the rest, as they say, is history.

Twodot meteorite

The brown and browner mottled surface contains few dramatic chondrules, but there are plenty of them even for a type 6 when you look closely.

 

Twodot meteorite

Measuring almost a foot in width (30cm), the Twodot meteorite is large enough to take useful curvature measurements with even crude tools.

Twodot is an H6 chondrite with a shock level of 2. About a third of the stone remained intact as far as I know and that would be considered the main mass. Two exceptionally large slices were removed from the center of the stone. The one pictured here that is in my collection is the largest surface area slice of Twodot, and highlights the cross-sectional orientation very well.

Twodot meteorite

The somewhat porous surface of the Twodot meteorite is obvious when eyed close up.

 

 

Twodot meteorite

The outer edges of the orientation show mild rollback tucking fresh material under the mushroom dome. The ablated leading surface produced a textbook-perfect shape to distribute the atmospheric forces of hypersonic travel though earthly air.

 

Twodot meteorite

As an H chondrite, there is plenty of visible metal sprinkled throughout Twodot. There are also some well defined chondrules of reasonable size in the picture. Not bad for a Type 6.

When I was young, I used to go deer hunting in the Twodot area so I am keenly aware of what it’s like wandering the opens spaces under that particular slice of the Big Sky. While my collecting preferences lean heavily on the older and less abundant witnessed falls with further prejudice for those with interesting cultural stories. Twodot is a special meteorite to me even though a weathered find. And until the Treasure State produces another stony meteorite, it wills remain very special to all of Montana as well.

Until next time….

About the Author

Martin Horejsi
Dr. Martin Horejsi is a Professor of Instructional Technology and Science Education at The University of Montana. A long-time meteorite collector and writer, before publishing his column The Accretion Desk in The Meteorite Times, he contributed often and wrote the column From The Strewnfields in Meteorite Magazine. Horejsi is currently a monthly columnist in The Science Teacher, a journal by the National Science Teachers Association.Horejsi specializes in the collection and study of historic witnessed fall meteorites with the older, smaller, and rarer the better. Although his meteorite collection once numbered over a thousand pieces with near that many different locations, several large trades and sales have streamlined the collection to about 250 locations with all but 10 being important witnessed falls.Many of the significant specimens in Horejsi's collection are historic witnessed falls that once occupied prominence in the meteorite collections of Robert A. Haag, James Schwade, and Michael Farmer. Other important specimens were acquired through institutional trades including those from The Smithsonian Institution, Arizona State University, and other universities.
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