Meteorite Times Magazine Contents Paul Harris
Featured Articles Accretion Desk by Martin Horejsi Jim’s Fragments by Jim Tobin Bob’s Findings by Robert Verish Micro Visions by John Kashuba Norm’s Tektite Teasers by Norm Lehrman IMCA Insights by The IMCA Team Meteorite of the Month by Editor Tektite of the Month by Editor
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Meteorite Times Magazine An Interplanetary Ambassador: The Gibeon Meteorite Martin Horejsi
Sometime late last century I purchased a chunk of Gibeon iron from Blaine Reed. It was a very well formed complete individual that contained many of the features I needed. Yes, needed. For this particular iron was going to earn its keep as a tool for teaching about the solar system. Since that time, literally thousands of students young and old have got their hands on this Gibeon as their first intimate experience with a real meteorite. So what were the features I selected for this teaching iron?
Whoa There! Backing up a step, I did not simply buy any old iron sight-unseen, nor get the most pounds for my bucks. Instead I considered what the specific teaching needs and demands on such a meteorite would be. Sure, waving around a square centimeter of SNC can be jaw dropping, but that’s more a shock of faith than a visceral reaction to physical interactions. What I wanted was something that the students could play with, yet not threaten the iron or their own safety. Plus the iron must be portable but massive enough to let gravity do the talking.
Got A Pic? Because the internet was still in diapers, Blaine Reed mailed me some Polaroid pictures of potential candidates given my list of needs. After a little back and forth, I settled on a 25 pound Gibeon of particularly solid construction with a lightly symmetrically and ovalish form. The surface was filled with quality and representative thumb printing, but absent of any extraneous protrusions. The smooth but undulating surface was appealing to the eye, and characteristic of iron meteorites without introducing rare but memorable features such as holes, orientation, protruding inclusions, or cut faces that can confuse the topic. While unique or unusual features are interesting and certainly part of the world of meteorites, they can also become the rule of the exception. In other words, those cool, valuable and highly desired bits of meteorite uniqueness can distract from the initial learning about rocks from space. For example, I once showed a handful of chondrite slices to a high school class only to have the teacher comment that she never knew that meteorites were so flat! Needless to say, I didn’t see that one coming. Or another oxymoron of meteorite identification is that most stone meteorites are attracted to a magnet…unless they are of the highly desirable achondritic variety. A side note on this sidebar is that early hot desert nomad trainers show the locals how to use magnets to ID possible meteorites. But it didn’t take long for the nomads to realize that the non-magnetic suspects might be the most valuable which is why the flood of achondrites appeared much later after the Great Saharan Meteorite Rush. And more than a few meteorite dealers scored big by buying the magnetic-attracted stones and getting the “duds” for free or pennies on the gram.
Spec Sheet The weight and shape of the iron were critical for what I had in mind. First, the weight must be enough to shock handlers, but not so much to prevent mobility. And the shape must prevent easy grip on the iron. Yes, prevent it. At 25 pounds, the iron is not something that can easily be picked up by a student, let alone with one hand which just happens to be my rule when the meteorite is at the center of a group of students. Adding to the struggle of lifting the iron is that it is fairly smooth and somewhat slippery from human hands and occasional cleaning and oiling.
When presenting the iron to a class of students from preschool to college-age, I usually pull the iron out of its bag and drop it a few inches onto a piece of carpet or desktop. The aggressive thud planted the seed that this thing is heavy, well actually dense. I then roll the iron around to show off its form, as well as demonstrate the intersection of explorative curiosity and respect the students must have for this particular meteorite.
Gibeon Can Vote Fast froward 20+ years, and the Gibeon is no worse for wear, yet has enriched many lives and impressed thousands of meteorite-curious students. As a representative of an asteroid, a meteorite, a model for the core of the earth and a possible building block of life, this a simple-shaped, molecularly-boring lump of nickel-iron metal, this humble Gibeon iron has done more than its share of work as an interplanetary ambassador.
Until next time‌.
Meteorite Times Magazine NWA 10731 a Fascinating Stone James Tobin
It is always exciting for me when I get the word back that a meteorite has finished being classified and is off to be approved. That happened several weeks ago for Paul and me. Three meteorites I had found while cutting a mixed box of stones looked unusual enough to warrant being sent off and classified. NWA 10731 as it is now officially known turned out to be a little gem of a stone. It has ended up with a classification of “L3-6 genomict breccia� but the story is more interesting since the stone was right on the edge of another classification. It was a single stone of 1439 grams. Nothing about the outside was unusual. It has a nice exterior, no cracks, solid stone with a generally light matrix and all its metal which explains the W1 weathering state it was given. As soon as I cut it I thought this one needs to be looked at better before we just slice it up and sell it.
NWA10731 had a normal weathered fusion crust with some shallow regmaglypts. There were places on the surface where mechanical wear had exposed the metal as bright spots. The fusion crust only covered approximately 60% of the stone. The broken surfaces had darken to a desert varnish color. Though broken, little of the meteorite’s original mass was actually missing from the stone. The first thing I noted when I cut the end off the main mass was the striking breccia. It was different then what we see many times. The textures in the several lithologies were widely different. The large clasts were distinctly different in color also. I immediately struck by how pretty it was. There was a reddish brown group of clasts, and a gray group, and masses of very dark almost black rock. There were large inclusions that were light colored and featureless which looked to have no visible metal. I could see that the reddish and gray areas were some kind of ordinary chondritic material but the dark patches looked like melt pockets. Much later when I looked at these under a microscope the metal in the dark patches was quite normal in regard to abundance, size and shape of the metal grains. Often in melt pockets the metal will be round blebs rather than the normal irregular shaped grains. Also a portion of the metal will often be extremely tiny round blebs mixed with the larger round or oval blebs. The metal in the dark patches of NWA 10731 was normal and more careful examination under magnification revealed that there were hard to see chondrules in the dark patches. This would also seem to rule out being areas of melt. When the work on the stone was done I made a comment about the dark patches to the classifier. I had just sliced up a batch of pieces and could not remember if the dark patches I was seeing had been so prominent in the two pieces I had sent for classification. I was assured that there had been dark areas in the samples and was given a very nice explanation of what the dark regions are. I will repeat that explanation here. “The metal and sulfide have been fluidized/melted and make up the material between the chondrules, so the area is opaque/dark, but chondrules are still visible.� So in a sense the areas are melt but not the same as the glassy melt seen in NWA 7347 or Chico where the metal is tiny blebs and the chondrules are melted away.
This is the contact between of one of the large black melt areas and the fragmental chondritic materal filling the space between the larger clasts of the breccia. The metal in the dark melt area has a normal appearance not showing the melting into round blebs common with many melts in other meteorites. Note the large inclusion of troilite on the left above center in the image. Some of the inclusions I had seen were igneous and free of metal and sulfides. There were several other types of inclusions I had not seen before sending the specimen off. I never seem to think about photographing the pieces that I send for classification. I can see at this late time in life that it is a great idea and will try to remember in the future. Another large inclusion in the sample was triangular shaped and turned out to be type 6 material. There were additional areas of type 6 material in the sample. However, the material of the main lithology turned out to be made of a mixture that contained 20% type 3 material.
These images show the type 3 chondrules that are mixed into the fragmental material in the matrix of NWA 10731.
These images show the type 3 chondrules that are mixed into the fragmental material in the matrix of NWA 10731. After I cut and finished the slices to a fine polish I took them to my macro photography station to image some of them for this article. What I immediately discovered was the large number of troilite inclusions that were in the stone. I have included several of the images here. Each piece I had prepared contained numerous small spots and two or three larger inclusions of troilite which is an FeS mineral. I found myself running to the Meteoritical Bulletin write up to see what it said about iron sulfide. It stated there was FeS everywhere, in veins, in melt areas, as rims on chondrules and inside of chondrules. There is something about troilite that I like. I am always pleased when I find it in meteorites be they stones or irons. I think it is the bronze color and the fine grainy texture. It is just very pleasing to my eye. And when there is metal on the side or partly enclosing the troilite inclusion that is just a bonus. I found a few of those during my imaging session on NWA 10731. The following images are of the troilite which is abundant in NWA10731. Some occurs as large inclusions and much is spread everywhere are tiny bits and amoeboid masses. Some mixed Ni/Fe and troilite inclusions are seen also.
I have marked the easily seen troilite in the area of this image to demonstrate the amount of FeS in
NWA10731. I don’t presume to understand all that has been included in the Meteoritical Bulletin write up on NWA 10731. There are numerous minerals that were found and I have not gone anywhere to see what they are. Maybe I will later. But the mention of metallic copper did get my attention. I kept my eye out for any while the slices were under magnification. I did not see any, it may be that the particles are very small. I would not know what to look for other than if I saw a coppery glint of light. But it is fun to know that it is in there still, metallic copper in meteorites is not very common.
These are two images in reflected light of the copper in NWA 10731. They were provided by Cascadia Meteorite Laboratory. In the first image the copper grain is small and associated with the “messy� troilite. In the second image below, the copper is a little nicer. The blue-gray chopped up grain is a chromite.
The write up on NWA 10731 is the most exhaustive report on any meteorite that I have ever submitted. And there was a bit of discussion before it was approved about how it should be classified. There were areas that were so borderline LL that it almost received a different classification of L(LL). And I understand that it is still being examined and could perhaps get changes after ongoing oxygen isotope work. Thinking about some of this as I prepared the pieces encouraged me to do a little nicer surface preparation. On an ordinary chondrite I would normally have left one side at probably 600 grit to show off the chondrules with the best contrast. And I would have finished off the other side to 1200 grit which is a low polished shiny surface free of most visible scratches and streaks from the other diamond laps. But these I finished to 1200 on the backside and I put a polish on the front with 50,000 diamond mesh which is a nice high polish. When they made it under the macro lens I was very pleased that I had done the extra work. I can occasionally image the structure of chondrules when the light is adjusted right and slices are finished this way.
Most of a part slice is shown in this image. Most of the characteristics of the meteorite are seen. The different lithologies and the type 3 mix as well as the igneous inclusions and FeS abundance are visible. A small amount of the black melt shows in diagonal corners of the image. I want to take this opportunity to thank Cascadia Meteorite Laboratory for all their work on NWA 10731 and especially Dr. Melinda Hutson and Dr. Alexander Ruzicka for the time they spent on this stone. These scientist are busy and have many responsibilities beyond their time in the lab. I want to be sure that credit goes where it is deserved to these hard working meticulous scientists. All most of us on the receiving end of their work ever do is cut off a piece and mail it away. I admit to being very excited about what was found. It always adds a lot to the meteorite for me to have it classified. I wish I could get all the stones studied, but that is impractical today. It is gratifying to know that this meteorite had some features not commonly seen and that some knowledge and information was added to our understanding of the solar system through its study. We have always thought that providing information and knowledge about meteorites had to be a large part of what we do as well the selling . I am happy that this meteorite is offerings some fascinating opportunities for study to the individuals that end up buying it.
Meteorite Times Magazine Part 2 – Tektite or Impactite or Obsidian Pseudo-tektite? Robert Verish
Preliminary results from quick tests with a handheld XRF show that you can tell the difference.
Recently I was able to get access to a hand-held XRF analyzer (a Thermo Niton XL2 GOLDD unit). After much delay due to hardware problems and scheduled maintenance, I was finally able to test the various specimens of tektites, impactites, and obsidian that were described in my March 2016 – Part 1 article, “Is it a Tektite or is it a Pseudo-tektite“. As I explained in my Part 1 article, “portable XRF analyzers” are becoming more common-place, and are affording the layperson cheaper and quicker spectrographic analysis of metal, mineral, and rock specimens. In the past, this kind of analysis required expensive equipment that was larger, more labor intensive, and time consuming, which would price the testing of mundane material (such as, obsidian and other natural glass) right “out of the market”.
Even with the very limited time that I had the XRF available to me, I was still able to test sixty (60) specimens of various tektites, pseudo-tektites, impactites, and a variety of volcanic glass (obsidian). The Thermo Niton XL2 can output its readings in the form of an .XLS file. With this file I was able to sort all of my specimens in increasing percentage of titanium (%Ti) composition. The report form of this sort (see below) essentially self-segregates the obsidian samples from the tektite specimens. In order to better show this self-grouping Iâ&#x20AC;&#x2122;ve color-coded the fields for ranges of %Ti that are above and below a certain arbitrary value (here, I chose 0.02%Ti), and another color for all values below a lower limit of detection (<) for this handheld unit. Prior to this testing, I had made the observation that earlier measurements of %Ti for obsidian and for tektites never appeared to overlap. The purpose of this testing is to see if these 60 additional measurements would continue this non-overlapping of %Ti values between obsidian and tektites. The results of these 60 additional measurements in essence show no overlap in %Ti values. Generally speaking (ignoring some â&#x20AC;&#x153;notable exceptionsâ&#x20AC;?), and as I stated in my Part 1 article: The results for actual tektites should have %Ti values that range above 0.2%, and the results for obsidian specimens will have %Ti values that are below 0.2%.
Impactites have shown a wider range of values, not only going well above 0.2%, but going below 0.2%, as well, thereby overlapping obsidian and tektites. This “fact” raises several questions which I would like to find answers, but that pursuit is outside the focus of this study. I’ve included impactite measurements here for the reader’s convenience, and only ask that this be remembered when my discussion turns towards a peculiar volcanic glass that I self-collected in Nevada, and that I am calling “obsidian” (but XRF readings suggest that it may actually be an impactite, which makes it one of the “notable exceptions” mentioned above). Again, if the specimens that I collected in Nevada are actually impactite, then all of the specimens that are actually obsidian are indeed “below 0.2%Ti”, and all of the actual tektites are indeed “above 0.2%Ti”, which shows that there is no overlap — see below: Index
SAMPLE
27
V-obs-mahog
29 31 57 59 60
NOTE
%Ti
purchased < LOD Mahogany obsidian purchased V-obs-snowflake < LOD snowflake obsidian V-obs-snowflake- purchased < LOD 120 snowflake obsidian V-tek-Troy-glass man-made glass < LOD tests + for obsidian V-tek-TX_Troy03 < LOD not tektite tests + for obsidian V-tek-TX_Troy04 < LOD not tektite tests + for obsidian
± 2 σ Ti Error 0.078 0.139 0.096 0.135 0.151 0.105
61 63 101 102 103 105 108 118 119 120 121 128 132
V-tek-TX-Troy09 V-tek-MoldaTroy06 V-tek-AmeriPhilipp V-tek-Apache V-tek-ApacheB V-tek-NormBedias01 V-tek-NormColumbi V-tek-NormSaffordA V-tek-NormSaffordB V-tek-NormSaffordC V-tek-NormSaffordD V-obs-Tobinmagnetic01 V-obs-Tobinmagnetic11
165
V-tek-A-8.17
166
V-tek-B-7.95
167 168 169 171 173 114 122 129 109 126 25 172 117 124 62 131 115
not tektite < LOD very poor quality < LOD Moldavite Amerikanite, < LOD Philippines obsidian < LOD obsidian < LOD tests + for obsidian < LOD not tektite Columbianite Safford, AZ obsidian Safford, AZ obsidian Safford, AZ obsidian Safford, AZ obsidian Black Rock Nevada obsidian Black Rock Nevada obsidian obsidian sold as tektite Hungary
0.105 0.112 0.101 0.103 0.112 0.138
< LOD 0.107 < LOD 0.106 < LOD 0.109 < LOD 0.147 < LOD 0.115 < LOD 0.11 < LOD 0.119 < LOD 0.109
obsidian sold as < LOD tektite Hungary obsidian sold as V-tek-C-7.64 < LOD tektite Hungary obsidian sold as V-tek-D-5.5 < LOD tektite Hungary obsidian sold as V-tek-E-4.12g < LOD tektite Hungary V-obs-Healds- not obsidian, nor < LOD not_obs tektite ?slag? V-obsBlack Rock < LOD BlkRckite20.9g Nevada obsidian Libyian Desert V-tek-Norm-LDG 0.131 Glass (tektoid) V-tek-NormZhamanshinite 0.136 Zhamanshin (impactite) V-obs-TobinBlack Rock 0.166 magnetic026 Nevada obsidian V-tek-NormDarwin glass 0.173 Darwin (impactite) V-obs-TobinBlack Rock 0.174 No_mag Nevada obsidian V-obs-wholeBlack Rock 0.176 stone Nevada “obsidian” V-obsBlack Rock 0.191 BlkRckite4g Nevada “obsidian” V-tek-NormRizalite, Philippines0.201 Rizalite B-side V-obs-TobinNevada, but tests 0.208 uncert + for tektite! V-tek-Rizapurchased Rizalite, 0.222 Troy05 Philippines V-obs-TobinBlack Rock 0.233 magnetic08 Nevada “obsidian” V-tek-NormMuong Nong 0.239
0.104 0.101 0.098 0.104 0.092 0.142 0.064 0.069 0.066 0.071 0.066 0.006 0.065 0.073 0.064 0.074 0.066 0.075
65 111 107 130 125 112 58 110 104 127 28 113 142 64 106 145 143 66 160 159
Muong V-tek-AustrTroy08 V-tek-NormIndochiB V-tek-NormBedias03 V-obs-Tobinmagnetic05 V-obs-Tobinimag01 V-tek-NormIrghiz01 V-tek-TX_Troy02 V-tek-NormIndochi V-tek-NormAustral V-obs-Tobinheated V-obsTektest2012 V-tek-NormIrghiz02 V-rck-Myst-TL29 V-tek-ThaiTroy07 V-tek-NormBedias02 V-rck-MystTL53005 V-rck-MystTL53002 V-tek-ThaiTroy07inclu V-imp-Lonar Crater-1 V-imp-Lonar Crater-1
158
V-rck-LV130525
98
V-min-myst05
99
V-min-myst05B
purchased as Australite tektite
0.24
0.071
Indochinite
0.24
0.075
Bediasite
0.247
0.07
Black Rock Nevada “obsidian” 0.275 Black Rock 0.276 Nevada “obsidian”
0.067 0.065
Irghizite (impactite) 0.298
0.068
purchased as 0.308 Indochinite tektite
0.072
Indochinite
0.311
0.074
Australite
0.313
0.077
Black Rock 0.316 Nevada “obsidian” purchased as 0.347 Indochinite tektite Irghizite (impactite) 0.388 Takysie Lake Pseudometeorite purchased as Thailand tektite Texas, Bediasite
0.068 0.052 0.08
0.406
0.07
0.463
0.067
0.477
0.071
Takysie Lake 0.492 Pseudometeorite Takysie Lake 0.534 Pseudometeorite oxide-rich inclusion 0.55 in tektite
0.074 0.071 0.08
India, impactite
0.786
0.136
India, impactite
1.173
0.106
probably man1.454 made “slag” titanite in ilmenite9.783 magnetite titanite in ilmenite9.935 magnetite
“NOTABLE EXCEPTIONS”:
0.099 0.112 0.181
Among the specimens that were measured with an XRF and gave readings “above 0.2%Ti”, the only notable exceptions were my very own self-collected Nevada natural glass specimens that I self-labeled as “obsidian”. But they may be something else. For instance, they could be impact-glass, and in that case their XRF readings wouldn’t be anomalous, and then they wouldn’t be a “notable exception”. Make no mistake, these specimens are not tektites. I had these same specimens tested by Jim Tobin, and they all failed to pass his criteria for being a tektite. All except for one small, round stone which Jim has labeled as “Uncertain”. I had no reason to expect this particular specimen to be any different from the many other opaque-black, non-magnet-attracting, round “Apache Tears” (or “marekanites”), that can be collected by the dozens along the margins of most playas. But, when this little stone underwent Tobin’s torch-test and it did nothing, that was much unexpected! It was heated beyond its melting point and it still did not change, which is a positive test for being a tektite. There was no cracking, or splintering, or white-frosting of the edges, let alone foaming of the glass, which is a positive-test for obsidian. Although I wouldn’t go so far as to say that “this proves it is a tektite”, I would say that, until a more sophisticated testing method is utilized, it is indistinguishable from a tektite. This finding could be significant because a recent hypothesis has predicted that, although tektites are found in mapable strewn-fields where the majority have densely fallen, there is no reason to rule-out that, once having gone sub-orbital, a few stones could have traveled farther down-range resulting in the possibility of these vagrant tektites having fallen far outside their “mapped strewn-field”, essentially anywhere. In time, as technical advances are made, and as we look closer and closer, we may find more and more “surprises”, such as this little black anomaly masquerading as an Apache Tear. As far as the other Nevada specimens are concerned, although this torch-testing excludes those specimens from being tektites, it doesn’t rule-out that they are impactites.
The Libyan Desert Glass (LDG) sample was a cloudy-whitish color. Among the tested specimens that gave readings for %Ti above threshold levels, but were “below 0.2%Ti”, which were populated predominantly with impactites, there were no notable exceptions. The LDG specimen gave the lowest reading, with the 0.131+/-0.064% value being just above the limit of detection for this unit. The lowest reading by a tektite was a Philippine Rizalite that gave a borderline value that was just above 0.2%Ti, but what was notable about this specimen was that one side had a coating that contaminated the measurment and drove the Ti value below 0.2%. Taking another reading from the back-side of this specimen gave a more accurate value and brought this specimen above the 0.2% level. Among the 10 samples that had values that were hovering around this 0.2%Ti-level (where 5 were above and 5 were below this arbitrarily selected value), there were six (6) that were my Nevada specimens. Bracketing my 6 specimens and the 2 Rizalites were an impactite (Darwin Glass) and a splashform (Muong Nong). These 10 specimens (which were 1/6th of the samples I tested) formed a field of results, which (when you consider the ± 2 σ Ti Error) define what I mean by specimens with “borderline” readings. For the reader’s convenience, I’ve highlighted in yellow the sub-0.2% specimens.
When I picked-up the Thermo Niton XL2 handheld XRF to conduct my testing, it was already pre-calibrated and pre-set with a lower limit of detection, which was somewhere below 0.12% for Ti, and which coincidently coincided with having the vast majority of obsidian specimens to give a “<” reading for %Ti. There were a number of notable exceptions here in this group, if you consider specimens being labeled as “tektite” but in reality being obsidian as being notable. For instance, my neighbor had a small collection of glass nodules that were labeled as “Tektites from Hungary”, which he had purchased several decades ago, but when tested they were shown to be obsidian. If you don’t consider these instances of misidentification as being “notable”, then there are only 2 specimens on my list that need to be discussed.
V-tek-Norm-Bedias01 A good friend and long-time tektite collector, Norm Lehrman, lent me a sample of every major category of tektite and impactite from his collection for the purpose of this testing. One of the many bags that he had sent to me was labeled “Bediasite”, but it contained three (3) samples. I debated whether I needed to analyze all three, because at first, they all looked so similar, but I finally decided to test all three. That turned-out to be a good decision, because the three test results were widely spread. In fact, the “Bedias01” sample tested “<” for Ti which means it tested too low to be a tektite. This caused me to re-examine the three samples very closely, and while using microscopic magnification, I eventually realized that there were differences among them. Hopefully, the reader can see the diagnostic differences in the above image. “Bedias02” has had its surface sufficiently etched to reveal the tightly-spaced laminations typical of tektites, whereas, “Bedias01” has on its surface a conchoidal fracture that reveals a cloudy inclusion that is often seen in obsidian but not in tektites. I’m not sure, but I think Norm was testing my identification skills, and if I passed, it was only “by the skin of my teeth”.
V-tek-Molda-Troy06 Another old friend lent me some specimens from his museum in Houston. Unfortunately, each of the specimens that were labeled “tektite found in Texas”, they all came back testing positive for obsidian. Fortunately, all of his purchased tektites came back testing positive for tektites. All except one, his little Moldavite. There was nothing about this little, PALE-green chip that would make you feel that it wasn’t a Moldavite (except that it was rather poor-quality), so it was a major surprise when it was tested and the reading came back %Ti too low to detect! I did a review of the literature and the lowest (published) value for TiO2 in Moldavite was 0.23% and coupled with the oft-mentioned fact by specialists that more than 75% of the Moldavite on the market is fake, a prudent course of action would be to treat this specimen as suspect and to hold it for additional testing. At best this specimen is a good example of the usefulness of a portable XRF to the Moldavite buyer/collector. Having said that, I should inform those who are analyzing their specimens of this statement by Tranka & Houzar (2002) : “The colouring influence of Fe3 in glass substantially increases with the increasing content of Ti and Mn (Volf M. B. , 1978: Chemie skla. SNTL, Praha). The relatively low content of titanium, nearly half content, in moldavites, rare georgianites, bediasites from Muldoon (and also in urengoites) is in all probability the cause of their higher translucency in comparison with other tektites.” So, keep this in mind while testing your Moldavite specimens, because if they are very pale-green, they may give low readings for Ti content.
These specimens, as well as many other examples of tektites and pseudo-tektites and impact-glass, were lent to me by our friend and fellow tektite-expert, Norm Lehrman. Their XRF readings are contained in the above results.
The %Ti was statistically too low and did not display for this Saffordite “D” (specimen #121), nor did it display for the other “A”, “B”, and “C” specimens.
The graph of the spectra for the Saffordite “D” (specimen #121) So, here is my conclusion: when properly analyzed, the results for actual tektites should have Ti values that range above 0.2 %, and the results for obsidian specimens will have Ti values that never go above 0.2%. So far, with all of the specimens that I have tested this has been the case. (Testing of additional specimens of natural glasses will continue). I have kept the discussion of “impact glass” to a minimum, mainly because I need to do more testing of impactites. So, I will be continuing to test “impact glass” (as well as, other natural glass), and will by recording and reporting those results here in future articles.
This specimen, as well as many other tektites and pseudo-tektites and impact-glass, were lent to me by our friend and fellow tektite-expert, Norm Lehrman, of the “Tektite Source“.
This particular specimen is highly-collectible because it has a beautiful pinkish-violet color in transmitted light. Unfortunately, that is not an appropriate color for a tektite. None of the samples labeled “pseudotektite”, gave readings above 0.2% for titanium. Acknowledgements. I would like to thank the editors, Paul Harris and Jim Tobin (of Meteorite Exchange) for access to their vast tektite and impactite collection. Jim Tobin for cutting and torching my samples. Jayson Coate for loaning his Healdsburg obsidian specimens. Troy Bell (of both the Houston and the Whiteside Museums of Natural History) for the loan of Tektite specimens from their collection. And to Norm Lehrman (of the Tektite Source) for his expertise and his technical insights on future tests that may be applicable to studying these intriguing glassy rocks. References: Tobin, Jim, 2011, Tektite Testing Revisited, Meteorite-Times. Pierce, Stephen E., 2002, A NEW METHOD TO DETERMINE THE DIFFERENCE BETWEEN TEKTITES AND OTHER NATURAL (VOLCANIC) GLASSES, an article in “From the Lab”, in Meteorite-Times. A NEW METHOD TO DETERMINE THE DIFFERENCE BETWEEN TEKTITES AND OTHER NATURAL (VOLCANIC) GLASSES“, by Stephen E. Pierce My review: The author was trying to promote a technique he called “Spectrophotometric signatures” over the other analytical methods of that time. Back then, it was more costly to do “chemical analysis”, and to do measurements just for Ti would never have been considered a cost-effective diagnostic test. Unfortunately, he turned-thumbs-down on the chemical method, because the results would be ambiguous since “the tektite and obsidian oxides overlap”. But that isn’t true for all oxides. And TiO2 (titanium oxide) is one of them that does not “overlap”. So, that is why I’m making the point that the ease of access to the current XRF technology has lowered the cost of this kind of analysis and has made this a viable diagnostic tool. TABLE D [reproduced here, from Stephen E. Pierce, 2002] MAJOR ELEMENT COMPOSITION OF TEKTITES AND OBSIDIAN (percent) OXIDES MICRO ASIA USA EUROPE AFRICA OBSIDIAN SiO2 64.15 73.06 76.37 80.07 71.05 76.78 TiO2 0.88 0.68 0.76 0.80 0.70 0.08 Al2O3 14.15 12.23 13.78 10.56 14.60 12.09 MgO 2.41 2.04 0.63 1.46 3.29 0.1 CaO 2.89 3.38 0.65 1.87 1.67 0.57 Na2O 1.63 1.27 1.54 0.51 1.71 3.79 K 2O 3.09 2.20 2.08 2.95 1.53 4.93 Fe2O3 8.37 0.60 0.19 0.15 0.18 5.60 FeO * 4.14 3.81 2.29 5.51 2.61 P2O5 0.72 NA 0.19 0.15 0.18 NA MnO NA NA 0.04 0.11 0.08 NA H2O NA NA NA NA NA 0.2 MICRO=Microtektites, N.A. strewn field, (Varekamp, 1982):Asia=Australites, (McCall, 1973) USA=North America, Europe=Moldavites, Africa=Ivory Coast, (King, 1976): Obsidian=Obsidian Yellowstone Park, (Hatch et al, 1972). *All iron reported as Fe2O3 :NA=No data available Volf, M. B. , 1978, “Glass Science“, Chemie skla. SNTL, Praha.. Trnka, Milan and Houzar, Stanizlav, 2002 , Moldavites: a review, Bulletin of the Czech Geological Survey, Vol. 77, No. 4, 283–302. Deutsch, A., Ostermann, et al, 1996, Nd-Sr Isotope Systematics of Impact-related Glassy Objects (Urengoites, South-Ural Glass, Zhamanshinites, Irghizites)
Meteorite and their Origins, Meteoritics & Planetary Science, vol. 31, page A37 The Thermo Scientific – Portable XRF website: https://portables.thermoscientific.com/xl2-goldd https://www.thermofisher.com/order/catalog/product/XL2GOLDDXRF XRF is a non-destructive analytical technique used to determine the elemental composition of materials. XRF analyzers determine the chemistry of a sample by measuring the fluorescent (or secondary) x-ray emitted from a sample when it is excited by a primary x-ray source. Each of the elements present in a sample produces a set of characteristic fluorescent x-rays (“a fingerprint”) that is unique for that specific element, which is why XRF spectroscopy is an excellent technology for qualitative and quantitative analysis of material composition. The X-ray Fluorescence Process 1. A solid or a liquid sample is irradiated with high energy x-rays from a controlled x-ray tube. 2. When an atom in the sample is struck with an x-ray of sufficient energy (greater than the atom’s K or L shell binding energy), an electron from one of the atom’s inner orbital shells is dislodged. 3. The atom regains stability, filling the vacancy left in the inner orbital shell with an electron from one of the atom’s higher energy orbital shells. 4. The electron drops to the lower energy state by releasing a fluorescent x-ray. The energy of this x-ray is equal to the specific difference in energy between two quantum states of the electron. The measurement of this energy is the basis of XRF analysis. Energy Dispersive X-ray Fluorescence (EDXRF) EDXRF is the technology commonly used in portable analyzers. EDXRF is designed to analyze groups of elements simultaneously in order to rapidly determine those elements present in the sample and their relative concentrations—in other words, the elemental chemistry of the sample. Interpretation of XRF Spectra Most atoms have several electron orbitals (K shell, L shell, M shell, for example). When x-ray energy causes electrons to transfer in and out of these shell levels, XRF peaks with varying intensities are created and will be present in the spectrum, a graphical representation of x-ray intensity peaks as a function of energy peaks. The peak energy identifies the element, and the peak height/intensity is generally indicative of its concentration.
Post Script: In my “Part 1” article, I made mention of “ferro-chrome-manganese”. Since then, I have tested about a dozen samples of ferro-alloys from my collection, and I yet to find any that contain chrome. Apparently, “ferro-chrome-manganese” is much more rare than I, and others, had expected (which explains why it is prized by collectors of this kind of material). In addition, the results of my testing suggest that ferro-silicon and ferro-manganese are two different TYPES of man-made material. My ferro-silicon samples are a compound called “iron silicide”, which means that the covalent bonds of that compound make it resistant to oxidation. Ferro-manganese, on the other hand, is an alloy which doesn’t prevent the metals from oxidizing. This explains why ferro-manganese specimens develop a black crust of manganese dioxide, whereas, ferro-silicon is relatively stable. Ferro-silicon – as well as, Ferro-manganese – – one of many varieties of Ferro-alloys – – Man-made Material – – “Slag”! Silicides, in Fulgurites and Ferrosilicon — Unusual Compounds Formed under Reducing Conditions in Nature and Industry My previous articles can be found *HERE* For more information, please contact me by email:
bolidechaser at yahoo dot com
Meteorite Times Magazine Tieschitz H/L3.6 John Kashuba
Tieschitz is interesting in thin section. In our sample, large and small chondrules are set apart by opaque matrix. Radial pyroxene and cryptocrystalline chondrules display aqueous alteration. One large chondrule contains several relict grains. We see chondrules that appear to be radial olivine darkened with fine included particles, probably amphiboles or other alteration products, and by rust stains. There is one chondrule containing finely dendritic olivine.
Overview 7.3 mm wide. A variety of large and small chondrules are set apart by opaque matrix. The brown radial pyroxene chondrule below and left of center has a lighter colored edge. â&#x20AC;&#x2DC;Bleachingâ&#x20AC;&#x2122; is the result of the aqueous removal of feldspathic glass from between the pyroxene laths. Tieschitz H/L3.6.
Large chondrule containing several ‘dusty’ relict grains – olivine grains with myriad minute dark inclusions. The chondrule is surrounded by a broad dark rim. Field of view is 3.1mm wide. Tieschitz H/L3.6.
An aggregate of fine mineral grains surrounding an opaque circular bleb of metal all surrounded by a dark rim. Dark radial olivine chondrule at top right. FOV=3.1mm. Tieschitz H/L3.6.
Radial olivine chondrule. It is darkened by many minute dark inclusions and by a rust stain (here, at top). The rim passes light more readily due to aqueous â&#x20AC;&#x2DC;bleachingâ&#x20AC;&#x2122;. FOV=0.6mm. Tieschitz H/L3.6.
Dark radial olivine chondrule at center. FOV=3.1mm. Tieschitz H/L3.6.
Radial olivine chondrule darkened by fine inclusions. FOV=0.5mm. Tieschitz H/L3.6.
Dark radial olivine chondrule at left and bright radial olivine fragment at right. FOV=3.1mm. Tieschitz H/L3.6.
Radial olivine chondrule darkened by inclusions and with outside bleached. FOV=0.9mm. Tieschitz H/L3.6.
Radial olivine fragment. FOV=0.7mm. Tieschitz H/L3.6.
Two quite different barred olivine chondrules at center. Barred chondrules derive from fully molten droplets. FOV=3.1mm. Tieschitz H/L3.6.
The same two barred olivine chondrules. FOV=0.9mm. Tieschitz H/L3.6.
Dendritic olivine chondrule below and right of center. FOV=3.1mm. Tieschitz H/L3.6.
Dendritic olivine chondrule. Diameter = 0.6mm. Tieschitz H/L3.6.
Dendritic olivine chondrule. FOV=0.4mm. Tieschitz H/L3.6.
Meteorite Times Magazine Splatform Tektite Basal surface textures Norm Lehrman
Splashform tektites largely assumed their geometric form during aerodynamic flight, giving rise to a wide variety of dumbbells, teardrops, patties, spheroids, and similar forms. Amongst the splashforms, there is a subclass which I term “splatforms” which show deformation of primary shapes suggestive of having “splatted” against some hard surface while yet very plastic.
In the last column of this series, I dodged the question regarding what splatform tektites may have splatted on. Like so many tektite topics, this proves to be a more challenging question than it might first appear. For years, I took it for granted that it was simply impact on the surface of the ground, but there are problems lurking in that assumption. The deformation involved clearly took place while the primary morphologies were still mostly molten. They had gooey interiors and solidified skins that were in the transition from stretchy to brittle. The areal distribution of good splatforms requires flight paths hundreds of miles in length. Consider the small sidesplatted teardrop at the left in the foregoing image. It weighs 6.7 grams. Such a small mass would have a very limited heat budget, particularly when passing through the sub-zero temperatures in the upper atmosphere. How could it retain sufficient plasticity to splat when it hit the ground after even a short flight? The “dragon-track” skin-split specimen splatted so flat that the brittle skin split revealing a stretchy, lowviscosity interior (exactly like a stretch tektite). Next to the right in the image is a large teardrop that splatted nose-first. Its tail telescoped into the molten center, leaving only its brittle tip protruding. This one was able to swallow the volume involved without the skin splitting, indicating it was still very, very hot at the time it splatted. The far right specimen is a hersheys kiss, also a nose-first splat, but less telescoped, probably due to the more limited heat budget of a smaller mass. Not only is the heat budget and long-distance flight a problem, but it is also noteworthy that not a single tektite known to me has any foreign object (i.e., a pebble or another tektite) embedded in its basal surface. (People sometimes get confused by ferruginous laterite adhesions that look like embedded pebbles. They are not). Nor have I ever seen the recognizable imprint of any foreign object marking a splatted surface. Early on I wondered if this might be explained by wet ground at the time of the tektite shower, but once again, the areal extent of splatform distribution, which includes southern China, Vietnam, Laos, Thailand, and neighboring areas, is simply too large to call on uniform ground conditions throughout. This was mostly all densely vegetated country as well. Where are the burned out limb casts or reed imprints like we see in Dakhleh impact glass? Where are the pieces that look like they draped across something they landed on?
The idea of a wet ground surface was inspired by the distinctive textures seen quite universally on the basal surface of strongly splatted specimens. In the first image, tops and bottoms are shown in the upper and lower rows respectively. I have seen this style of deep pocking on the base of molten lead or aluminum that has pooled on bare ground. I presume that this is due to jets of steam and gas scorched from the baking soil beneath the molten metal. But, if we are forced to seriously question the premise of splatting via impact on the earth’s surface, what alternatives can we consider? Perhaps the best candidate is the hard face of the sky itself. In this context, water-skiing offers experiential insight: take a spill on a high-speed corner, and the surface of the water feels more like a solid than a liquid. I vividly recall skipping across the surface, and feeling relief when the water finally softened enough to take me in! In the case of meteorites striking even the rarified edges of earth’s atmosphere, it is common for them to shatter as if it was stony hard. Perhaps in the extremely high-energy environment of a major impact event, the flying blobs of glass build up a cushion of compressed air against the frontal surface. The pocking of the frontal surface might be quite equivalent to steam-jet pocking beneath molten metal. There, the steam jets attack the interface metal and are the moving part of the system. In the case of a compressed air cushion collecting in front of a high velocity projectile, the air is relatively still as the projectile moves into it. The results might be highly similar in either case. This whole process would happen very early in the event, while everything was still rosy hot and flying through a proximal sky. There would be no pebbles to engulf, no tree limbs to cast and incinerate, and nothing for the plastic glass to drape around. Those with a flight time of more than a few minutes were likely cold on impact.
Here are a couple more fine examples of splatforms with obvious upper and lower surfaces and very clear development of basal (or frontal) “pocking”. Teardrops of the sort shown in the two adjacent images are the morphology subject to the most extreme
splatting. I think of them like water-balloons of molten glass. It seems that these primary shapes were hitting the wall (whatever it was) at nearly random orientations, ranging from nose-first to flat on the side (but I havenâ&#x20AC;&#x2122;t recognized any that were splatting tail-first). I find pieces like those pictured in this article inspiring. They tell their story in graphic detail. Each one is a top-shelf museum piece, a superb example of its kind. And they are worthy protagonists, offering clues written bold and frozen in stone to help us understand what went on in the day they were born!
Meteorite Times Magazine SPACE ROCKS MAGAZINE Paul Harris
After much thought I have decided to publish a new quarterly magazine about hunting, collecting, and the science of rocks from outer space. I will not be accepting yearly subscription payments, only payments as each individual issue is published and ready to mail out to the subscribers. If you have any questions please send me a private message or contact me using the email listed below. Your support is what will make this magazine a success for us all in the meteorite community. Regards, Michael Johnson Editor-in-Chief, Space Rocks Magazine
August 2016 issue of SPACE ROCKS MAGAZINE Click Magazine To Purchase
Please submit your article with photos to: spacerocksmagazine@gmail.com
Meteorite Times Magazine Imilac Pallasite Paul Harris
Our Meteorite of the Month is kindly provided by Tucson Meteorites who hosts The Meteorite Picture of the Day.
Contributed by jnmczurich, IMCA 2391. jnmczurich writes: This end section is a part of a 19 kg mass, found within the Imilac strewn field in 1986. One of the pictures shows the original impact crater with the 19 kg individual/fragment looking some few centimeters out of the soil of the crater basement. Diameter of the crater is 80 cm. Submit Pictures to Meteorite Pictures of the Day
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Once a few decades ago this opening was a framed window in the wall of H. H. Nininger's Home and Museum building. From this window he must have many times pondered the mysteries of Meteor Crater seen in the distance. Photo by Š 2010 James Tobin