I do not cut meteorites for anyone other than our business as a general rule. But, my friend Jason Phillips of Rocks From Heaven, contacted me about a newly recovered meteorite from Mexico that he wanted to get cut open to see its insides. So I said, “Sure send some pieces, and I will slice them.” We had a conversation over many emails the next few days, and he let me know that he would send one large stone, one medium stone, and one small stone. I had a moment of thinking about Goldilocks, but that passed quickly. The stones also arrived quickly in just a couple days. The large one was just that. At about four kilos it was one of the largest meteorites I have cut. The medium stone was covered in thick white caliche but had a nice shape and was over a kilo in weight. The small stone was a nice fusion crusted corner of a stone. I was to find out as the work went on that the small stone was a fragment of the large stone and the source of the type specimen used for getting the meteorites classified. The name submitted to the nomenclature committee for the meteorite was Quitovac.
The stones were found at a newly discovered strewnfield in Sonora, Mexico by a man metal detecting for gold. After finding the first stone, some more hunting produced additional finds. A total of five stones have been found as of the time of this writing with a total weight of 9,112 grams.
There had been no discussion about cleaning the meteorites, but they needed to be cleaned, so I cleared that with Jason and set about making them pretty. The caliche was removed carefully from the spots it covered on the large stone and then it was washed and scrubbed with a toothbrush and alcohol. It cleaned up very nicely. I thought about removing all the reddish brown rusty patches and uncovering the fusion crust. I could make it nice black and dark gray again but decided to leave it in a more as found but cleaned condition. The large stone was only to have the broken side sliced off and smoothed up. The other two pieces were to be sliced up completely. It was more important therefore that they be cleaner since having nice black fusion crust where possible on all the slices was a great improvement over the rusty brown and caliche covered edges the slices would have if I did not clean them. Cleaning up the slices later is much more work and dangerous since there is a higher likelihood of the fusion crust chipping off.
The small stone was easy to clean. Since it was once part of the large stone, its exterior was the same. A few patches of caliche and the red/brown spots. I removed the spots with my special process and exposed the nice black fusion crust below. The small stone was done in a very short time ready to cut. I had sliced the broken side off the large stone by the time I cleaned the small piece, so I knew that it was going to be weathered inside also. The matrix of the large stone was stained light and dark browns with one area in the center that had remaining lighter original gray. Some of the metal grains were absent in areas of the face. But the stone was very attractive with a pleasing exterior color and was covered with regmaglypts hinting to perhaps some orientation. Two large and interesting mixed metal and troilite inclusions were cut through in slicing off the broken face. Many chondrules could be seen easily even though the meteorite Jason said was an L6 which often have few visible chondrules. I expected that the small stone when completely sliced would produce similar brown matrix slices.
I turned my attention on the second day of work to the totally caliche covered medium stone. There was not a spot on the surface that exposed the fusion crust. I could see, however, that the stone was complete except for one broken side. That broken spot though also covered in caliche did tell me that this stone was not darkened by weathering and was going to make very fresh looking slices. Some of the stones had been found buried while others were on the surface. This likely explains the difference in the way they weathered. I began removing the caliche, a process that took two or three hours to complete. But a magnificent fusion crusted stone was exposed. Since it was going to be sliced, I removed all the discoloration on the surface. I recovered the black fusion crust so it would look nice on the edges of the slices. The before and after images shown here will show the difference.
I was going to be keeping a portion of the meteorite for doing the cutting and asked to keep one of the endpieces of the medium stone, and it is shown in the next image. I also kept the broken side sliver of the big stone which I hope will make both a piece for my collection and maybe a couple of cabochons as well. There are parts of it that have no remaining metal and are very dark brown. Meteorites in that state are not too attractive as collection pieces but are ideal for jewelry stones that will never further rust and cause problems to the wearer.
I took one very thin cut of about 1.5 mm during my slicing of the small stone to use in making thin sections in the future. I thought there was enough surface area that I could dice it into pieces for four thin sections. The thin sections would be from the same mass as the official type specimen. That is pretty cool and unusual.
I made the first cut into the medium stone expecting that it would be much fresher than the other two pieces. I was not disappointed, it was very fresh looking meteorite material. It was nearly white in color right off the saw which leaves a slightly rough surface. I expected that they would make beautiful very light gray slices when finished off on the diamond lap. The metal was 90+% intact, and there was little staining beyond small brown specks and a brown rind right near the edges of the slices.
In the distant past, the standard for meteorite slices was about a quarter inch in thickness. Many of the micro mounts sold over the last couple decades are rather cube-like because they have been cut or broken out of such older ¼ inch thick slices. But today with a much larger group of collectors most slices are cut thinner to create more pieces and to fit containers such as membrane cases not made for things that are thick. One rarely sees ¼ inch thick cuts anymore. I had a decision therefore about how thick to make my cuts. On lunar and Martian material the idea is to get the most number of slices and the largest surface area with the lowest weight since the material has traditionally been very expensive. There is more waste with more cuts, but that is what has been happening with high-cost meteorites. I did not have to cut this material thinly, but I also do not make ¼ inch thick cuts anymore either. I chose .135 inches as the setting I would use for the cuts. When lapped on both side that would yield slices around one-eighth inch in thickness or just a little less.
I took off an endpiece and then another and then one more. There were regmaglypts and beautiful fusion crusted areas that I wanted to preserve in the endpieces pieces and certainly on the one I had selected to keep for myself. Then I remounted the stone on a holder so I could slice it like a loaf of bread from one end all the way to the other side. The image below shows the slices obtained. My blade is .008 inch in thickness but creates a kerf of about .010 -.012 inches so very little waste actually in this type of slice after slice cutting. I usually am at about 5% cutting waste with another 5% or so being lost in lapping. But by keeping the bigger fusion crusted endpieces the total waste was very low on the cutting of the medium size stone. I ended up creating over forty slices from the medium stone with a final weight at the end of preparation of 1097.8 grams.
I finished the medium stone slices off to 1200 grit on the diamond lap. They did turn out as can be seen in the images a nice light gray as if they fell yesterday. Well, not yesterday maybe. On three of the slices are sections of a very large object that from its smoothly oval shape looks to be a chondrule about 7/16 inch in diameter. I was excited when I hit that with the saw. I shot some pictures with my phone and sent them off to Jason. I was keeping him up to date pretty well with images. I knew he was excited too to see the inside. There was a generous amount of metal scattered across the slices of the medium stone. Certainly in line with what could be seen in an L chondrite but more than is often seen. In the slices of the small stone, much of the metal had weathered out just as expected.
As can be seen in the images above the chondrules maybe easily visible but they are quite altered and clearly blending into the matrix of the stone. There are no distinct edges. They were on their way to fading into the matrix.
The small stone was sliced according to the same criteria; two endpieces with great fusion crust were made, but the slices were cut just a little thicker. I set the saw at .150 inches and finished off the slices were just over one-eighth inch thick. However, because the stone was weathered and stained, it was much harder and more solid than the light gray fresh material. I finished the slices to 1200 grit and then polished them on one side with 50,000 mesh diamond on a felt disc. They ended up with rich chocolate colors. There were 17 pieces created from the small stone and a total weight of 543 grams.
The large stone was a bit of a chore to cut. When you go to the desert and pick up a chunk of pretty agate or jasper or petrified wood it is just a broken mass. You clamp it in the vise of the diamond saw and chop slabs off it. Not so with meteorites. They are almost always masses with round ends and sides that often refuse to be clamped without special attachments or a lot of fiddling around. Also, care must be used not to crack or break the meteorite by applying too much force with the vise. I ended up flipping my vise up out of the way and cutting a piece of ¼ inch plywood into an exact rectangle that would fit on one side of the saw blade. I used the short wall of the saw top as a guide to push the plywood against. I mounted the meteorite to the board with masses of hot glue after tilting the stone so the broken surface was the most vertical that it could be. In the end, I took off a slice that faded off to nearly nothing right after passing the one bump in the surface I had to remove. I do not think I could have cut off any less than I did. But the stone was also too large for my rotating lap. I had gotten a very nice smooth cut so I decided that I would smooth and low polish the surface by hand grinding it on a big sheet of thick glass. I never throw anything of worth away. It is a character flaw and habit inherited from my parents who grew up during the Great Depression. So all I had to do was go to the shelf where sheets of glass are kept and get one saved from an old copier or printer I had dismantled. It was nearly a ¼ inch thick and certainly strong enough for me to grind the 3-4 kilo stone on. I poured out some 600 grit aluminum oxide on the glass and wet it with methanol. Wearing vinyl gloves, I ground it smooth to a low polish in less than an hour. It was like being a teenager again making telescope mirrors. I washed the stone with alcohol and dried it off. The flat surface looked very nice.
I did not want to polish the face for it would lose most of the little contrast it had for seeing the chondrules. Also, I would have to figure out another unique setup to polish it. I could put it on the vibrating lap and let it run for a couple of weeks to polish beautifully. But that would be long exposure to water which I felt was not good for this somewhat weathered stone. Same result though of not being able to see the features of the meteorite once it was dark in color. The image below of the surface shows that it turned out nice and that the details of the meteorite are still visible.
I took my normal care with the drying of the slices as they were cut. I used chlorine free purified water with a little alcohol as the coolant in the saw. Just enough alcohol to “wet” the water so it would flow better along the sides of the blade and down in the kerf. Dried the slices with a towel after removing them from the soft landing zone below the blade. Put each slice in a bowl of 100% alcohol to soak until at least the following slice was finished cutting. Then it was into a can of fresh silica gel to sit until time to lap. Lapping is the same; each slice is dried and soaked in alcohol after each grit. This time I used just the 360 grit to start since they were quite smooth right off the saw. Then just a touch with the 600 grit and 1200 grit disks to remove the marks of the previous stage of lapping.
I knew that I wanted to write this article about the cutting project, so I was taking all the images along the way. I also took the following video of the cutting of one full cut on my home made saw. The video is about 2 minutes long but may be interesting to watch and see how meteorite preparation is done. I am pretty happy with my saw still after a few years of use. It gives me all the control I always missed in selecting a thickness and repeating a thickness of cut. It also makes feeding the meteorites through the blade very smooth and controllable. I had tried using stepper motors and other things but have returned to a threaded rod screw feed. I have made thousands of cuts with the saw and am sorry to say I did not take the time to clean the saw for the video.
All the pieces except the 3500+ gram big stone were put into silica gel immediately after a soak in alcohol following cutting. It is a chore to open the container of silica gel 40-50 times, but it is essential that the slices get dry as soon as possible after running in the coolant water for the 5-10 minutes the cuts take. Also, the fresh material was much more porous than the hard solid weathered material, and I wanted to do no harm. That is the biggest reason that I do not accept cutting jobs. Whenever I have cut for people, I worry about the other person’s meteorite too much. I think about the embarrassment there would be if I had to tell them of a catastrophe on the saw. Like maybe their stone fell apart on unseen cracks. Just do not want to have to make that call ever. But everything went very smoothly on the cutting of the Quitovac stones.
Just a few days after Jason received the big stone and all the slices back. He asked me if I could clean the other three pieces found of the meteorite. He was happy with the cleaning of the first batch. I said sure. I enjoy the cleaning part. I told him in an email it is like opening Christmas presents. Removing the caliche and exposing the fusion crust is like tearing off the wrapping covering something beautiful underneath. Here are before and after images of those other three pieces.
I have little doubt that more pieces of Quitovac will be found. It is starting much as Gold Basin started by gold prospectors finding meteorites. Only now they are aware that the hot rocks are valuable too. It was really cool being in at the beginning of this meteorite’s appearance on the market. I weighed the slices and placed them in baggies with a generous amount of silica gel, packed the materials up really safely and sent them on their way. I hope that many collectors will enjoy this new meteorite. It was a fun project.
I had some time even with the holidays so on a Saturday morning I made the thin sections. I did get four nice full slide area pieces from the thin slice I had cut off the small fragment used for the type specimen. The image below shows the completed thin sections in a membrane case. The images after that are of chondrules in crossed polarized light. They show nicely how the chondrules are fading into the ground mass and are loosening up on their way to becoming just aggregations of mineral crystal grains. But they are still together now and still visible.
After writing all of the above information the meteorite became official in the Meteoritical Bulletin about a month later on December 18, 2017. The Quitovac name was accepted and the full classification data is summarized as follows. Five pieces were found with a total weight of 9,112 grams. I got to work on all of them which was really cool. The final classification was L5 which I heartily agree with after cutting 60 slices. The condrules were too visible for the average L6. Shock stage is 2 and weathering stage is 2. The description of the meteorite in the Meteoritical Bulletin is that of the weathered 51 gram mass that was the same as the large stone and the corner fragment also from the large stone. The fresher material cut from the medium stone is not going to be anything like what is described but is the same material. The second batch of three stones that I cleaned only remain a mystery as to how they appear inside.
