PROBABLE IMPACT FEATURES: BALD SPOTS, IMPACT FRACTURES, STARBURST RAYS, RADIAL RAYS?, STRETCH/SPLIT TEKTITES
Probable impact features are common in Indochinites, bald spots are extremely abundant, starburst ray features are common and stretch tektites are very rare. I have not observed good impact fractures. Impact features in Philippinites are less common, but bald spots, starburst rays and impact fractures do occur. In Australites impact features are not recognised, although possible impact fracturing may occur and brittle breakage likely occurred.
INDOCHINITES: Bald spots are very common on Indochinites, forming areas devoid of sculpture. They are simply areas of spalling. Spalling on Indochinites was very light when compared to Philippinites and Australites. This is because Indochinites commonly began re-entry whilst molten and formed a thin brittle crust in the later stages or re-entry. A solid brittle crust could then be spalled.
I believe the edges have simply 'flaked off' in the same way as core formation. On my tektite tests page it is interesting to see the same thing happening there as the heated tektite cools. Note that later on, when the tektite is naturally etched in the soil, it only becomes pock-marked on the original surfaces (the middle of the anterior and the posterior surface). The edges of the anterior surface (where flaking occurred) are left largely unscathed by etching. The edges are effectively 'faceted' and thus present a smooth and impenetrable surface to corrosive waters.
ABOVE LEFT: A dumbbell from Thailand with bald spot at the base. ABOVE RIGHT: An Anda from Vietnam with bald wedge-shaped areas around the edges of the specimen.
WEDGE-SHAPED BALD SPOTS
As observed above in the Anda disc-shaped specimen above, the bald spots will often form wedge like features (sometimes with a hollow in the middle). As discussed above, my feelings now are that these likely represent thermal shell loss or 'flaking' in a similar way to core formation. Certainly the wedge-shaped bald areas represent the anterior of the tektites.
ABOVE LEFT: The base of a head shaped dumbell that has a wedge-shape. This exploded around a bubble. ABOVE RIGHT: A teardrop specimen with a wedge shape formed by sagging and then spalling during re-entry.
or just etching?
ABOVE LEFT: A biscuit shaped Philippinite showing ?fracture marks on the posterior surface.
ABOVE RIGHT: A photo of a hard boiled egg after being dropped. Hard boiled eggs probably have a more elastic interior compared with the plastic interior of the tektite, but in both cases the exterior is brittle.
STARBURST RAYS OR STARSCARS
See the Stretch Tektites page for an update on these features.
ABOVE LEFT: Starburst Rays ABOVE RIGHT: Radial Rays
ABOVE: Two excellent examples of starburst ray features in Thailandites.
ABOVE: A bent and flattened teardrop with starbust Ray features at the point of impact.
See the Stretch tektites page for an update on this feature.
ABOVE: Good examples of radial rays in tektites from North Vietnam.
Stretch tektites are discussed in more detail on my new Stretch tektites page.
ABOVE: A teardrop tektite from Vietnam showing Anda sculpture and a clear split. Possibly not showing enough angular distortion to be a true stretch tektite, but clearly broken exposing a plastic interior.
Very rarely collision features are observed (not to be confused with aerodynamically formed navels). These clearly demonstrate the plasticity of the body. The smaller body strikes the viscous plastic larger body and is partially incorporated. This could have occurred either during flight or immediately after landing. An excellent example can be found in the Meteorite Times at http://www.meteorite.com/MT_links/2003/March/Tektite_of_Month.htm.
ABOVE: It is possible that in this Anda tektite a small tektite collided with, and was incorporated into, the larger body. This feature may, however, simply be a secondary feature due to etching of an area where shell loss occurred.
Closely related to the aforementioned Starburst Ray features are Stretch Tektites, made famous by Nininger and Huss, 1967. These have also been referred to as Taffy Cores. These effectively formed in an identical manner to Starburst Rays, by having a hardened shell that is ruptured on landing. To qualify as a stretch tektite, however, the specimen must show a convincing angular distortion, opening up the crack. Good examples are to be found at www.tektitesource.com.