Most of the readers of this article know by now that I cut a large number of meteorites during a year. I have been particularly busy lately. For the last couple of months, I have been cutting every day. I have stopped cutting for anyone else all this work is just for the Meteorite Exchange our company.
I thought for this article I would take you on a journey through a month in my lab. It started with a 300+ gram Allende. The first thing I noticed on this stone was the very large chondrule sticking halfway out of the surface. It is the largest chondrule that I have ever seen in an Allende stone and over the years I have cut many good size Allende meteorites.
I got about forty slices from the stone with two end cuts of course. I lapped them on both sides to smooth them and then lapped one side to 600 grit. Polishing Allende is always an iffy situation. Some stones benefit from the polish but most of the time the stone is just darkened and suffers a reduction in contrast and chondrule visibility. I tested one slice by polishing it and did not like the results so I left the slices at 600 grit a nice pre-polish stage. I rubbed the surface four times with an isopropyl alcohol-soaked tee shirt rag to remove the carbon powder from cutting and lapping. This step makes a huge difference in how Allende looks when dry. I put all the slices into silica gel beads and let the alcohol get fully absorbed. I save the Allende dust from cutting and lapping so I was not done with Allende until the wash down of the equipment was completed.
I had several dozen slices of NWA 13758 a great-looking R3 chondrite to finish. They were sliced and smoothed but needed to be lapped with very fine grit and polished if it helped the slices. This time 1500 grit from a worn-out disc was the best surface for the most visibility. 3000 grit did not make much of an improvement over the 1500 grit. Finishing these slices was the end of a batch of work I had started several weeks earlier. I had another batch of meteorites already in my “IN” tray. These were all more exotic.
I have to clean the saw and lap after doing chondrites before I start working on Martians and Lunars. I have to clean after each of these as well. We save the dust from the individual meteorite names separately.
I cut and prepared two Shergottite stones and a Nakhlite stone. The following image shows the slices from the two Shergottite meteorites. Both the stones were good-sized NWA 12269 individuals. Some of the slices from the second stone were still wet from cutting when the image was taken and appeared dark in the picture. It is a pretty greenish-gray color with the dark brown and black crystals showing well.
I cut the small 9.3-gram Nakhlite (NWA13669) next and got several slices. It is a friable stone and I did not lap or polish the slices. The sheering forces in the lapping and polishing steps would have torn the fragile little slices into crumbs. My blade is very thin and I feed slowly with an infinitely variable digital speed controller of a stepper motor so there are no significant lines on the slices anyway. They turned out nice though small. Having a Nakhlite in a collection even a small piece is a big deal since they are so rare.
Next came a change over to lunar meteorites with of course a cleaning to get the martian out of the equipment. I had a good size NWA 11182 that had been cut in half before we bought it.
It looked rather bland on the surfaces we received so I rotated the stone and cut through the two pieces a different way. I could see on the outside that there was some color and interesting rock on the other parts of the stone. I did not want to get several more slices of the featureless material if I could cut through a nice mix of the rock. This turned out to be a great decision. All the slices had beautiful colors. NWA11182 is the most colorful Lunar I have ever cut. I have at this point cut about fifty lunar stones totaling about 5 or 6 kilograms and none so far had the rich spectrum of colors of NWA 11182.
These are the slices I was able to get from the two pieces of NWA 11182. I lapped and polished all the slices finishing off at 50,000 mesh diamond.
This is one of the full slices of NWA11182 when it was finished. I love the reds, browns, and maroon colors it has, especially after working with white, grays, and black in most other Lunar stones.
Then of course there was another cleaning of the equipment so I could cut 24 small 1.8-4 gram lunar stones of NWA 11474. Up until recently I would have just ground a flat window on these size stones and lived with the waste that was created. But I worked out a method to hold and cut the small stones utilizing the same processes I already did with big stones. I have for decades attached the meteorites to aluminum mandrels so that I could precisely move stones slice after slice using a dial micrometer to control the thickness of each cut. I just needed a device to hold tiny meteorites the same way.
Here is what I did. I went to the garage and cut a piece of ½ inch aluminum rod the length of my standard aluminum tubing mandrels, about 6-7 inches in length. I turned down the outside of the rod until it was precisely the diameter that slides into the mandrel holder. This was necessary because ½ inch aluminum rod is often not actually ½ inch. In this case, it was about 9 thousandths of an inch oversize and did not go into the mandrel holder. After getting it to the correct diameter I milled a flat on one spot so I could properly drill a nice straight hole in the side of the rod. This hole I then tapped with threads so I could screw in a locking knob. I then bored a hole down the end of the rod nicely centered and well past the depth of the locking knob hole. Actually, I bored this hole about 1 ½ inch deep and a diameter of 1/8 inch. A final 45° chamfer on the end of the rod with the knob and a perfectly flat face on the opposite end. The machine work was done on the “micro mandrel holder” as I call it.
The final step in my new try at holding tiny meteorites for cutting was to make the tiny mandrels. That was easy. I took medium size nails with heads and 1/8 inch shanks and cut off the pointed end. The pointed end is always larger than the shank and would not have gone into the 1/8 inch hole. I ground the cut end flat, smoothed, and deburred it with a file. It went in easily and without any wiggling into the aluminum holder. I repeated the nail making until I had a nice batch. They would lock tightly in place with the knob. Now I could precoat the heads of the nails with dop wax and later attach tiny meteorites to these micro mandrels. I could still move them laterally through the blade as always. I would get two endpieces and one or two slices from all the tiny lunar meteorites.
At this point, I guess I should say that the dop wax I use in no way damages the meteorites. It melts at a low temperature and yet it is hard when cooled. It also completely dissolves away in isopropyl alcohol leaving no residue. It can not be used on some meteorites that are friable or porous but is suitable for most meteorites. I handle the few meteorites that are unsuitable for dop wax using other methods.
Here is an image of the little lunar (NWA 11474) meteorites attached to the tiny mandrels. The bead is approximately one centimeter on each side. The next image is of the tiny mandrel holder in the saw and one NWA 11474 lined up with the blade ready to cut off the end.
Well, as the following image shows the new holder worked very well. I was able in a short time to cut 24 small NWA 11474 fragments of Lunar meteorite into 60 end cuts and slices. Even though the image only shows about thirty cut pieces the photo was taken after cutting just ten of the mounted stones. The slices were easily lapped to 600 grit on one side and polished to 50,000 mesh diamond on the other. The numerous end pieces were finished to 50,000 mesh as well. The waste in lapidary work for the 24 piece project was 17%. Which for 60 cuts was very good in my opinion compared to the loss in grinding flat faces on the 24 lunar meteorite pieces. The window grinding would have produced higher waste than the cutting, light smoothing, and polishing of the new method. Also, I would grind a great amount of meteorite off to get even a small polished window. The picture shows that cutting allowed me to get large polished surfaces by carefully aligning the tiny meteorites on the mandrels.
All the description in the previous paragraphs works for only my saw but it might spark an idea for someone else. I am getting pretty old and I don’t mind so much giving up a secret or two now and then.
After one more cleaning of the saw and lap, I moved on to cutting a batch of eucrite slices. The business was going to buy 400 grams of a stone I had gotten in partnership with Jason Phillips a few months ago. It was officially published in the Meteorite Bulletin in October 2021 so ready for sale. It is a cool eucrite meteorite mostly showing a gray matrix but some pieces are a light golden orange shade. It was a sturdy stone that cut well and though porous as most eucrites are it took a high polish. To fill the 400-gram order took almost 80 slices and consumed five of the stones in my half of the purchase. I picked nice-looking solid cutter stones, but not the real gems from the 1500 grams I had of NWA 14370. Still several of the ones I cut had fusion crust on portions of their surface.
As the month ended I had two more large slices of Shergottite to dice up. It was
an easy job as the large slices were already polished on one side. But a big final job for the month was the slicing of a 300+ gram NWA 13788 Lunar. It is a different-looking stone when cut. All dark inclusions with low contrast. There appeared to be a bit of fusion crust in spots on the stone. It was the hardest darn rock I have cut in a long time. Difficult to lap as well. But after a few hours of work, I got the slices shown in the next image.
So that’s a summary of a month in my lab. I took a few days off here and there but mostly I was working all month. I cut a few hundred slices and lapped them on both sides and I polished one side on most. There was a lot of cleaning this month of the saw and lap. Much time is consumed in decanting off the water until I got a mud of meteorite dust drying in old photo development trays. Time is consumed in gathering, sieving, weighing, bottling, and labeling the various dusts. The exotic meteorite dust we sell. The more ordinary dust I still collect and use in ceramics. I am looking forward to experimenting with the eucrite dust to see what colors I can make adding it in clay and glaze. All the meteorite slices and endpieces have to be wrapped carefully and put in boxes for safety. It does not sound like a big deal but it takes a bit of time to wrap or layer with bubblewrap hundreds of meteorite slices. These extra tasks fill up the month of cutting so that it is harder to say I am retired. But this is more fun than work and I get to handle and make beautiful the rarest material on the planet and that is quite special.