Archive

“The first piece was found on Oct. 6, 2016, by Mr. Yanzheng Wang and Jifa Li, workers from a nearby oil field, who were searching for wind-eroded stones on the desert. The find site is 15 km NE of the Mountain Huoyanshan, which was noted in the famous 16th century novel, “A Journey to the West,” as having emerged from pieces of charcoal on fire falling from Heaven. 18 more pieces were collected from a strewn field of 2 × 1.5 km² during the following days. These irons weigh from 100 g up to 8.9 kg, with a total mass of ~45 kg. The news was leaked soon, and people rushed the desert to search for the irons with metal detectors. It is estimated that thousands pieces with a total mass of ~700 kg have been collected” (Meteoritical Bulletin no. 106).

With a band width of only <0.035 mm, Huoyanshan hides its beauty in the submillimeter range. Viewed with a loupe or stereo microscope, the iron reveals a unique, cryptographic pattern, perpetuating in bizarre cuneiform. Huoyanshan is hard to acquire, difficult to etch, and even more challenging to photograph, yet truly one of the most rewarding meteoritic irons to work with.

.

History: Found at 10:20 am on fine grained grano-diorite pediment. The flat, disk-shaped mass was stuck vertically in the ground, one third of the mass protruding from the soil.

Physical characteristics: A single, shield-shaped mass with brown and black colors. Cut face reveals a metallic unweathered interior.

Petrography: (J. Gattacceca, H. Pourkhorsandi, CEREGE): The etched section shows a polycristalline kamacite aggregate with crystal size to 550 μm. Abundant euhedral schreibersite 10-20 μm in size.

Geochemistry: (M. D’Orazio, DST-PI): Composition of the metal (ICP-MS) is Co=0.455, Ni=5.54 (both in wt%), Cr=76, Cu=125, Ga=67, Ge=191, As=4.4, Mo=6.2, Ru=25.8, Rh=2.72, Pd=1.67, W=3.33, Re=1.94, Ir=22.6, Pt=29.0, Au=0.39 (all in ppm).

This is a disk shaped iron with intriguing weathering pattern. Chemical erosion has reduced the initial surface and produced a set of protruding spikes up to 10 mm long.

History: Found in November 2015 exposed on the surface by artisanal miners while prospecting for gold between Tehmet and Djado in the Tènéré Tafassasset. Click here for full find documention and report of associated masses.

Physical characteristics: The 52 kg mass is 39 × 25 × 18 cm and has the shape of a longitudinally split cone with the cone section showing minor concavity while the opposite surface is distinctly convex. Numerous regmaglypts measuring 1-3 cm across and 1-1.5 cm deep are present, and at least one troilite inclusion is observed. The specimen is coated with a thick layer of dark brown desert varnish.

Petrography: Polished sections display a well-developed Widmannstätten pattern of a medium octahedrite with a mean kamacite bandwidth of 1.0±0.2 mm. Neumann bands are visible within kamacite. Schreibersite and graphite are absent in the sections observed. Troilite is present in the form of rounded and bar-shaped inclusions ranging from 2-20 mm across the longest axis, partly surrounded by thin swathing kamacite. Fractures up to 1 mm wide penetrate the meteorite along the kamacite lamellae and are filled with terrestrial oxides, otherwise the interior weathering is very moderate. Fusion crust and heat-affected zones are mostly absent.

This is partslice of 272 g, polished and etched on one side.

Found by Luc Labenne while searching fragments of the Imilac pallasite near La Mina Escondida in 2000. The 13.8 kg mass before cutting had average dimensions of 27 x 19 x 10 cm with a surface texture of small, circular shallow depressions, which is the characteristic weathering pattern of Atacama iron meteorites. This slice shows a bright etch with well defined Brezina lammellae.

New iron meteorite find from the Mauritania-Algeria border, of which I acquired the single 4.9 kg mass from the finder. The compact mass shows an attractive wind polished blue to olive drab desert patina, as it is characteristic of several other iron meteorites from the Adrar region in Algeria. The polished and etched surface reveals geometrically arrayed rhabdite plates and several generations of Neumann lines, a characteristic of most hexaedrites. The iron has been classified at the University of Alberta, Canada.

Geochemistry: (C. Herd and G. Chen, UAb) Ni=5.7, Co=4.6 (both mg/g); Cu=142, Ga=74.1, As=5.4, W=2.8, Ir=7.7, Pt=27.2, Pd=1.6, Ru=18.8, Re=0.53, Au=0.5 (all μg/g). Obtained by ICP-MS using North Chile as a calibration standard.

.

Like many other meteorites from Northwest Africa this meteoritic iron has a misty find history. In spring and summer 2008 several Moroccan meteorite dealers started to offer individuals of a new meteoritic iron. While two sellers could not provide any background Information, one seller at the Ensisheim/France meteorite fair in June 2008 told us that to his knowledge, the irons represented new finds from the area of the Ziz IAB complex meteorite (NWA 854). The Moroccan dealer was so kind to inform us that a lab analyzing the metorite on his behalf had arrived to the conclusion that the new material is structurally identical with Ziz (NWA 854). The same dealer on our request was so kind to forward us the certificate issued by the Etudes Metallurgiques et de Traitment Thermique (EMTT). The judgement of the EMTT, as meanwhile confirmed by the lab, refers to a basic structural indentity of the new meteorite with other coarse octahedrites of the IAB-complex only (of which Ziz is one). This, however, is also true for most of the other 218 meteorites in this large group. Macroscopically there was strong evidence that the newly discovered masses represented a different fall.

The above image shows a 1,873g specimen of the recently found iron meteorite while being cut on a diamond wire saw. Both an endcut as well as two slices for classification purposes were expertly cut and prepared by Marc Jost in Switzerland. As can already be seen on the untreated cut surface the meteoritic iron displays a number of irregularly distributed inclusions.

As the polished and etched surface of the pictured cut section shows, the new iron is intersected by numerous silicatic inclusions which make up to 45 volume percent in some of the masses recovered. The silicatic inclusions are rich in olivine with crystals up to 2.25 mm in diameter. These inclusions are one of the reasons to doubt that the newly discovered irons reprensent part of the Ziz meteorite (NWA 854).

We have contacted the current owner of what appears to be 90 percent of the original Ziz finds who confirmed to us that none of his idividuals contained any silicate phases. We also contacted the Etudes Mettalurgiques et de Traitment Thermique (METT) in France in this matter, which is the lab that worked on the original Ziz irons. Mr. Dransart from METT was so kind to confirm to us that none of his samples of Ziz (NWA 854) contained any silicate inclusions.

Besides the inner composition there are certain other features which suggest that the new irons in fact represent a different fall. Most probably from a different find location as well (the Ziz river runs for more than 300 miles through eastern Morocco and continues across the border through a large part of Northwestern Algeria). While the Ziz (NWA 854) irons display an almost fall fresh appearance with smooth regmaglypted surfaces only coated by a chestnut colored patina, the new irons are sometimes heavily eroded by the environmental forces.

As can be seen in the images, the texture of the iron surfaces is alternating from undulating surfaces smoothened from atmospherical ablation to a coarser pattern, where corrasion (sand abrasion) has eroded up to ~2 mm of the original material (No α2 zones could be found on examining the etched cut surfaces). Iron surface areas that were in situ protected from corrasion have developed a chestnut colored desert patina. Iron surfaces altered through corrasion, which represent the majority of the surface, show a matt-finished slightly olive luster in which the lamellae boundaries are apparent. The boundaries of iron and silicate portions are exaggerated through chemical and mechanical weathering. Obviously, the silicate portions have lost a higher ammount of surface material in this process. The described surface alterations suggest the involvement of a considerable ammount of wind born sand. But the more critical fact is that it takes some time until these erosion features can be observed on an iron meteorite. Given the new irons have indeed been found in the region of the original Ziz finds, then their respective fall appears to be orders of Magnitude older, or otherwise, their find location must represent a considerably higher erosive environment.

An extensive paper titled “Expertise and Analysis of a Sample of Ziz Meteorite” (EMTT, 2000) on the Ziz (NWA 854) iron meteorite was kindly provided by fellow meteoriticist Marcin Cimala from Poland. One of the inereresting results the EMTT presented is the fact that the spectrometric analysis determined an unusually hig ammount of germanium (640ppm) in NWA 854.

Considering our doubts concerning a pairing of Ziz (NWA 854) and the recently found material, we decided to submit a representative sample of the new material for classification under MetSoc requirements. The classification results published in Met. Bull. No. 98 show different values and the meteorite was declared a different find and received the NWA-number 6203. This is the classification result:

Petrography: (C. Herd and G. Nadeau, UAb) The meteorite contains abundant silicate inclusions. The metal consists of coarse-grained (~5 mm width) equigranular kamacite grains with 120° grain boundaries. Neumann lines are visible within individual kamacite grains. Small (sub-mm) schreibersite grains are present within some kamacite grains and at grain boundaries. Silicate inclusions consist of irregular, mm- to cm-scale masses of fine-grained (<0.2 mm) material intergrown with kamacite. Terrestrial oxides decorate grain boundaries and fractures that penetrate well within the meteorite interior.

Geochemistry: Mineral compositions (all mol%): Silicate inclusions consist of homogeneous olivine (Fa_4.9±0.2), low-Ca pyroxene (Fs_6.9±0.3Wo_1.8±0.3), clinopyroxene (Fs_3.0±0.1Wo_44±1), and plagioclase (An_15.7±0.1Ab_81.2±0.1). Also associated with the silicate inclusions are abundant troilite, kamacite, schreibersite and graphite, the latter either fine-grained massive or cliftonitic (as intergrowths with troilite). Modal abundances in the one silicate inclusion studied in detail are approximately 30% olivine, 15% low-Ca pyroxene, 15% Ca pyroxene, 15% graphite, 10% troilite, 10% iron oxides (terrestrial), 3% kamacite, 2% plagioclase and trace schreibersite. Bulk Composition (metal): INAA data (J. Duke, UAb): Ni = 6.28 ± 0.04 wt%, Co = 0.441 ± 0.003 wt%, Ga = 81.2 ± 0.6 μg/g, Ge = 377 ± 34 μg/g, Ir = 3.55 ± 0.04 μg/g, Au = 1.51 ± 0.02 μg/g, As = 11.0 ± 0.2 μg/g, W = 0.72 ± 0.13 μg/g, Re = 0.33 ± 0.04 μg/g (uncertainties 1σ, 68% confidence level).

Classification: Iron meteorite, IAB main group, low shock, moderate weathering. Silicate inclusion mineralogy is consistent with IAB-MG. The lack of Widmanstätten pattern precludes structural classification.

Many more masses have been found in a glacial moraine since the first discovery of a single meteorite in 1906 by Mr. Carl Henriksson. Muonionalusta is known for its striking Widmannstätten pattern. Because of the chloride-rich soil the Muonionalusta meteorites are recovered from, the iron tends to rust, usually from the edges towards the centre. This fullslice was kept for several weeks in an acetone bath and neutralized with an NaOH bath after the etching process. It remains fairly stable since.

Shield-shaped mass with distinct regmaglypts on the trailing surface. Until 2010, several hundred specimens were recovered from the Taza strewnfield, inluding many dozens of kg-sized regmaglypted masses. Meanwhile, the find location is depleted. A two-week Russian expedition with state of the art metal detecting equipment that was conducted in Spring 2014 yielded no further finds.

The second collection specimen is a hield-shaped mass with distinct regmaglypts on the trailing surface. Until 2010, several hundred specimens were recovered from the Taza strewnfield, inluding many dozens of kg-sized regmaglypted masses. Meanwhile, the find location is depleted. A two-week Russian expedition with state of the art metal detecting equipment that was conducted in Spring 2014 yielded no further finds.

Oriented shield shaped mass of similar appearance to the Cabin Creek meteorite. The breast side is covered by deep regmaglypts still sheltering remnants of fusion crust on their bottom. The regmaglypts originate from the broad apex of the shield and shape into distinct furrows towards the edge. There are no regmaglypts on the concave trailing edge of the meteorite. Exceptional specimen and certainly the best oriented Campo del Cielo meteorite we have seen.

Polished endcut of the Chinga ataxite. Fragments of this meteorite were discovered in the Chinga river and its tributaries by prospectors searching for gold in 1913. Several expeditions yielded more than 250 specimens until present. Today the location is exhausted and only very few meteorites are still beeing found. Although scientists have tried to locate eventual craters the fall of the Chinga meteorite might have caused no impact structures were found. Based on the deposits the Chinga meteorites are found in it is estimated that the fall took place between 10,000 and 20,000 years ago. Several researchers argued that Chinga fell on a glacier before it was transported to its current find location. The meteorite belongs to the ataxites and has a nickel content of 16.4 percent. This particular specimen has been etched but no Schliren bands were found. The photo shows the unetched polished surface.