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Norm’s Tektite Teasers: (Part one of three): Indochinites: The Classics

This is my 41st column for Meteorite Times, and I just realized that in my enthusiasm for tektite oddballs, esoterica, and rarities, I have never written about the most important group of all, the classics. If you had to choose just three Indochinese tektites to anchor your collection, they would be these: a patty, a dumbell, and a teardrop.

Figure 1: Classic Chinese and southeast Asian tektite morphologies. Teardrops: 120.0, 69.0, 22.9, 8.1, 8.3, and 3.7 grams. Patties: 442.7 (!), 222.8 (rt), 111.3, 14.4 grams. Dumbells: 411.7 (!), 92.3, 95.3, 17.7, and 12.4 grams.

It is important to understand that these are proximal splashforms (I like splatforms) that show clear evidence of ductile deformation and little or no evidence of thermal ablation. These “classic” forms do not directly apply to Philippinites or Australites, even though they were sourced from the same event. (stand by for parts 2 and 3 in this series; see Figure 2).

Immediately after impact, blobs of glass would have contracted into oscillating spheroids of high-temperature, low-viscosity melt entrained in the turbulent mushroom cloud. Those that fell close to the impact were flattened by interaction with the atmosphere. Those that lofted higher and further, cooled with minimal frictional compression at high altitudes, and are now found in the Philippines as spheroids. Smaller stones flew farther still, suffering the effects of thermal ablation. Only the Indochinites and Lei gong mo (Chinese tektites) exhibit clear plastic deformation.

Oddly, although the spheroid was the ancestor of all morphologies, it is not at all common to find spherical tektites in China or the southeast Asian parts of the strewnfield. They mostly deformed into patties . Many of the patties exhibit thin centers and thicker rims, suggesting that they were spinning like Frisbees. Blobs that got lop-sided sometimes spun like propellers, forming dumbbells. As the story goes, dumbbells sometimes parted in the middle forming teardrops. In the proximal region, all three morphologies remained sufficiently plastic to deform (“splat”) or flatten against the wind resistance of their fall through the waning plasma fireball.

It should be mentioned that the largest specimens pictured in Figure 1 are of world-class size. (Note the 1 cm scale cube at lower center left). The big dumbell is the largest known. The 400+ gram patty is a monster, but I have seen others of this size pictured. One was being used as the base plate for a wooden door in China. My friend installed a new door for them in exchange for the pivot stone. I couldn’t talk him out of the truly gargantuan concave patty! I really don’t like remembering not getting that one.

If these are the fundamental tektite shapes, what is their typical size when not part of a size-distorted collection? All of the monsters are from China, chiefly the Guangdong region. Still, the modal size is around only 50 grams, or twice that for patties. The modal size for SE Asians is smaller yet, with no monsters.

Figure 2: Geocaricature relating zonation of Australasian tektites. This article deals with the proximal Indochinese splashforms and their classic morphologies.

 

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