It would come as no surprise to any long time reader that I love everything about Meteor Crater. I love the history of the investigations and I love all the varied rocks from the site. Over the years I have gathered a few things that while not meteoritic themselves are from the crater. For me this ephemera makes for much of the fun of collecting. I have this kind of stuff for many meteorites; but not to the extent that I do for Meteor Crater.
I was very pleasantly surprised by an email a few months ago from a friend that knows of my obsession with Meteor Crater. She told me that she had an old canvas rock sample bag with writing on it that was filled at the crater. She said it had some residue of rock and silica powder still in it. She asked was I interested in having it. I said Yes, I would love it! A few days later the bag arrived in the mail and with it two baggies containing the rocks and powder. The bag had writing on it which told the story of its use.
The bag was used to hold specimens of coesite bearing sandstone from the main shaft dump site in the center of Meteor Crater. A little harder to read is the place that the specimens are being sent to. It reads:
Part of Shipment
To Max Plank Institute
From Dump of Main
Shaft, Barringer Crater
That is not the proper German spelling of the city name but likely what would have been used here in the US. And the use of the name Barringer Crater though not that unusual is mainly restricted to the geological and meteoritical communities. The general public universally uses Meteor Crater. I do not know much beyond these details. I don’t for instance have an exact date that the bag was filled. But I can figure out a rough range. The writing is done with broad tip markers a portion is red and a portion in black. So the bag was filled after the invention of the felt tip marker pen. The first commercially viable felt tip pen was the “Magic Marker” in 1953 followed by the “Sharpie” in 1964. Coesite was discovered originally at the crater in 1960. It seems likely the bag is from the burst of research on the crater in the late 1960s through the 1970s.
There was just 5 grams of fine white silica flour in the baggie. I moved it to a small glass vial. There were just 11 small pieces of the metamorphosed sandstone. But it came from the main shaft dump site which is very cool. That location is behind fencing now. I have a few samples I was allowed to gather of similar material. But they came from the dump next to Shaft #2 across the playa area from the more famous main shaft where the boiler and steam engine remain. Shaft #2 is the only one of the original shafts that has not been filled with anything and is still available for research. Having a few bits of rock and rock flour from the Main Shaft was a nice addition to my collection.
The powder is just what you would expect to see from the crater. It is so fine that it coats the inside of the glass vial with a dust layer. I will put it under the microscope someday to check how shattered the individual quartz grains are.
The 11 stones are all quiet small. But they are clearly showing the characteristics of the moderately metamorphosed sandstone. It was struck by the cosmic hammer blow and squeezed. This variety of rock from the crater has a sort of layering but not like any ordinary sedimentary rock. The layers if you want to call them that have been described as having a platy appearance. The layers are short sections that overlap with others that are also short in length. None of the pieces from the canvas bag have any signs of real melting as the more highly shocked sandstone from Meteor Crater does. Since the coesite is created without extremely high temperatures samples put in this bag were intended to be free of the vesicular glassy variety of rock. It would have been great to get a few more pieces of the vesicular material because I have very little of it. But I am so happy with having received these.
As I said I do have a small amount of the more highly altered sandstone. It is characterized by vesicles and sometimes has glass lining the bubbles. I have presented images of vesicles with threads of glass bridging them before. But here is an image of a typical piece of this material that Barringer called Variety B of the altered sandstone.
Meteor Crater has very little truly melted material. The closest material is the impactites. There just are no objects like the stringy, teardrop and rope-like glass bits found at Zhamanshin, Henbury, Wabar or many other craters. Instead the impactites from Meteor Crater are small chunks of poorly fused, bubbly dull luster rock that look like small volcanic bomb. There is nothing really shiny or glassy about them. The impactites were really the only material that was not recognized by the first investigators. They are found at a few locations around the crater and out onto the plains. Unlike shiny black irghizite type crater glass these are easily hidden among the rest of the crater rubble. They are various shades of tans, grays and browns, there are subtile differences between find locations. Below is an image of an impactite where the melted dark brown material is encasing a chunk of lighter material which looks to be shocked sandstone.
Years ago I took one of my larger impactites from Meteor Crater and cut it in half. I selected this one based not just on its larger size but that it was one with greater magnetic attraction to a magnet. Impactites regardless of the crater they come from fascinate me. Especially the ones that contain melted metal from the asteroid. The metal blebs do not show up in the first image below. It was shot to show the structure and the bubbly nature of the rock. Note the inclusions of native rock that are incorporated into the blob of melted rock. The second image shows the nice scattering of shiny metal. Impactites do give us a glimpse at how really hot and awful an asteroid impact site would be for any living thing nearby. Liquid rock would be flying around and attaching itself to other bits of rock and anything else in the area.
The lack of truly glassy material at Meteor Crater has been a question to answer. The event was far larger than Wabar or Henbury or others where really shiny true glass formed. What caused it to not form at Meteor Crater. The thick layer of sandstone certainly provided plenty of source material for glass. The thick layer of Coconino sandstone may also have been the reason that the glass did not form. It was also the aquifer hundreds of feet thick that caused the crater to immediately become a lake after the impact. Did the tremendous amount of water in the rock prevent the formation of the high temperature fine glass objects?
At Meteor Crater it was not just the melted rock that made it a terrible place to be. The vast majority of the asteroid was vaporized and when the metal vapor cooled it turned into tiny droplets of nickel iron. These tiny bit of metal were seen in soil samples very early in the investigations of the crater. Their true significance as representing the greatest part of the asteroid was not recognized until far later by H. H. Nininger. Called “ nickel iron spheroids” there are still after 50,000 years countless numbers of them in the soil around the crater. They are all tiny but even with tiny things there is a range of size. The image below is of a group of what could be called large size spheroids. The very small ones weigh 2-3 milligrams. And the larger ones in the image weigh around 5 milligrams. They do get much smaller in size and weight.
These were spheroids that were collected by Dr. Nininger during his years of living and working near the crater. He sampled the soil everywhere around the crater and came up with some numbers for the amount of meteorite material they represent in the entire region. To me this would be a math nightmare; to calculate the density at the large number of sample sites and then work out the average density of the tiny particles over the whole region and get a number in tons of original mass. So many assumptions would have to be tested by field work and specimen collection. Just figuring out how deep to dig the samples and do it the same every time was a challenge. When you read what Dr. Nininger wrote about the project it was a very difficult task. There are several different meteoritic materials in the soil samples. Little bits of iron shale that has weathered off of larger iron masses and broken down to tiny grains were in the samples. Also there were tiny bit of what he named “sluglets” believing them to be tiny meteorite fragments or splinters that had weathered to this tiny size. They were distinct from the spheroids and oxide bits. All of these magnetic products had to be cleaned, then seperated from each other so they could be weighed, nickel tested and ultimately analysed for their total chemical makeup. All this effort makes my Nininger spheroids pretty special little things. I am glad I got a few thousand of them years ago.
There was a time in the distant past when the crater could be hiked around and hiked down into. But that was nearly half a century ago. Paul and I had the great honor to spend a day in the crater floor and to hike around it a couple times a few years ago. I got to see all the locations that I have written about in several books. The floor of Meteor Crater is an amazing place. It is silent in a way we never experience in normal life. And the feel of the soil as you walk on it is unique. The crater was a lake for thousands of years after the impact. The crater floor we see today is the top surface of about 90 feet of lake deposits. When the crater was a lake there were fresh water mollusks living in it. They have left their shells behind. These shells can be seen as one walks about. The rock layers of the crater also have shells from much longer ago when the whole region was under water. Those fossils can be seen in the rocks when hiking on the slopes. But the tiny fresh water animal shells are very cute. An image of a couple is presented below.
They say that nothing is done until the paperwork is finished and that is true with meteorite collecting. We get specimen cards and COAs and we print out information from the Meteoritical Society Database. Sometime meteorites have a very historic past or there was research or other work done. So there are papers and reports and newspaper articles about them. These become part of what is collected along with the meteorites themselves. Over the years I have collected a great many of the articles, pamphlets and books on Meteor Crater. Some are not too special and are filed in alphabetic order by author name. But a few stand out. My original copy of Barringer’s 1909 paper with Standard Iron Company stamped on the cover and pencil notes in the margins is special. And the original “Proceedings of the Academy of Natural Sciences” from 1905 with the Barringer and the Tilghman reports on the crater is very special. This was the first release of information to the scientific community. All the debate begins with their papers. I love that I have the originals. But that set of books is but a part of the materials that surround my Canyon Diablo meteorites, all these other things add so much to my knowledge and enjoyment of the actual chunks of space iron.