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  H5-melt breccia

TKW 405 kg. Fall not observed. Found 2016, Agadez, Niger.

The find coordinates provided by the MetBul are 200 km NNW of Agadez, near the Uranium Capital of Niger.

 

Steve writes:

I was recently talking with Scott McGregor about his July 19, 2023 post on Tassédet 004, thanking him because I was just finishing up one on that very meteorite too, and now I didn’t have to. But he said the more the merrier, and he encouraged me to go ahead and submit it to Paul for posting anyway. So you can blame Scott for this one!

Tassédet 004 (sometimes also referred to as Tchifaddine) is an H5 chondrite impact melt breccia discovered in 2016 near Agadez, in the African nation of Niger. It is a large fall, and happily, a lot of material has been made available to collectors. The four pieces shown in Photo 1 are representative of the kinds of variation seen in this fall: some pieces exhibiting smaller or no amounts of melt; others having more; and yet others consisting almost entirely of pure melt, like the 9.6 gram vesicular/pumice-like individual shown in Photo 2 (in Photo 1, the melt appears as a lighter gray compared to the darker parent material).

Additionally, the metal found in this meteorite seems to vary between pieces too. Scott’s slice exhibited an almost equal mix of nickel-iron and troilite that appears almost "granular". In this MPOD, I thought I’d share some examples of other variations in metal and melt that I’ve seen in this meteorite.

The slice in Photo 3 weighs 121.9 grams and measures 128 x 93 x 4 mm; it exhibits metal blebs and large regions of dark melt with islands of parent material seemingly floating within it. The slice in Photo 4 weighs 219.9 grams and measures 133 x 126 x 4.5 mm – unlike the melt in Photo 3’s slice, the melt in this one contains significant amounts of finely distributed metal. Photo 5 offers a blowup of a portion of Photo 4’s slice that, in contrast to the slice in Photo 3, exhibits melted material appearing to flow around and within the parent non-melted material.

[Unlike Scott’s slice, these are more polished and as a consequence did not photograph well, so glancing reflected light was used in an attempt to better show the characteristics of the melt.]

In several of my slices and half-stones, the metal within the melt has pooled. This pooling is especially apparent in Photo 3’s slice, as well as the 235.8 gram halved individual in Photo 6 (the latter measures 84 mm across the longest cut dimension and exhibits both spherical and irregular metal pooling in the melt that bisects the stone). Photo 7 offers several additional views of the exterior of this piece.

The characteristics of the pooled metal seems to vary in each of my pieces. All of the metal aggregates in Photo 3’s slice display the "granular" structure seen in Photo 8’s animated GIF blowup of the large bleb at the top of Photo 3 (Scott and I have discussed whether this apparent granularity is from much finer threads of troilite separating the nickel-iron, or whether the thin separation is a consequence of something else). Alternately, Photo 9 and Photo 10 show crossed-eyes 3D images of some of the metal in Photo 6’s half-stones (Photo 11 and Photo 12 provide the corresponding red-cyan anaglyphs); all of the metal blebs in this particular piece – which has an appearance more similar to Scott’s example than, say, Photo 3’s metal – almost universally appear to be an obvious mix of nickel-iron and troilite (it’s much more evident in Photo 9 . . . the metal in Photo 10 has less troilite that’s harder to see – especially given that while the troilite appears much more bronze colored under the microscope, these images didn’t accurately capture the true colors).

[I should point out that none of these pieces were treated with acid or enhanced in any other way, so the appearance of the metal is simply a consequence of different rates of recession during polishing.]

There were also some fun vugs in a few of these pieces. Probably the most unique are the pair in Photo 13’s 3D crossed-eyes image (and Photo 14’s corresponding red-can anaglyph) – these can be seen to the left of the large metal bleb at the top of Photo 3’s slice and appear to be coated with some fairly shiny brownish silicate material exhibiting an intriguing bumpy texture. And if one looks at about the 10:30 position from the major bleb in Photo 8, an example of a glass-lined vug can be seen.

Finally, Photo 15 shows a complete 210.6 gram, 61 x 56 x 37 mm individual with a unique metal vein running along the length of the stone that protrudes on the opposite side as well, suggesting some form of this vein might run through the entire piece (this was the first of a dozen pieces of this meteorite I eventually acquired – after all, one can’t have too much melt breccias, or just about any meteorite for that matter!). I may try to get it x-rayed to get a better idea regarding what this vein might look like.