Australite Shapes page4

George Baker wrote of these forms found near Port Cambell 'These are all very special forms of tektites not encountered among the other known tektite-strewn fields of the world, the rarity and unexcelled character of these well-preserved, complete to nearly complete, unique types of tektites cannot be overstressed'.

The term 'mini tektites' was adopted byDon McColl and Guy Heinen in their article titled 'Ablation and Mini-Tektites' in Meteorite February 2005

They are very thin small forms in which the central core portion is very reduced in relation to the flange and in some there is no central core remaining so that the form can be called a 'flying flange'. They are the thinnest and weigh the least of any complete tektite! Many are quite unlike the normal range of australites.
It is suggested that some of these could have formed from spalled fragments of stress shell which broke off larger tektites but maintained enough velocity to continue melting, but if this is true you would expect to find a far greater number especially if you can imagine the amount of tektite material 'flaked' from the original primary bodies resulting in the 'core' types. It has also been suggested that they are the final remnants of ablated small primary bodies which entered the earths atmosphere with stable aerodynamic orientation at supersonic velocities.
It is not believable that the larger primary bodies have been reduced in size to this extent during their brief flight through our atmosphere but it may be possible that very small primary bodies also entered the atmosphere and gave rise to some of these 'mini tektites'. If they are from original tiny primary shapes then it seems incredible that these extremely light- weight tiny tektites managed to fly in such a tight group formation all the way from SE Asia and all land within a small area of sometimes only 50 metres by 50 metres! A mini dumbbell shape which I found does tend to suggest at lease some are due to tiny already formed primary bodies entering the atmosphere along with the main shower. I would tend to think that the larger perfectly symmetrical round discs with central cores are from tiny primary bodies but that the very tiny often folded mini tektites of unusual shapes could be derived as a secondary product from larger ablating flanged type australites. It seems hard to imagine that perfect round shapes would have time to evolve from the material rapidly being swept backwards in the wake of the falling tektite as surface tension would not have a chance to act on this ablated , viscous material before it cooled and solidified.

One observation I would like to note here is that I recently found a group of maybe 30 of these rare 'mini' tektites in an area in which I also found larger 'flanged' type tektites including two fully flanged buttons and many fragments of flanged buttons. In this particular area 'cores' were nearly totally absent except for one small core. Even the fragments I picked up had evidence that the tektite material had tended to 'flow' showing ring waves rather than flaking. Maybe within certain tektite showers the chemical composition of the tektite material was just slightly different enabling the 'flowing' of the material and the formation of more flanged types including these mini tektites. Or heating up of the tektite on entry was slower so that there was less stress and spallation but more gradual heating of the whole body and flow. I was amazed to find a large dumbbell with flanges in this area which more commonly would have formed into a dumbbell core and also a fragment of what would have been an amazingly huge flanged button if it had survived! In areas where there are all 'core' types these mini tektites are much rarer and this suggests that they may not have formed from the 'spalled material' from cores but may be more associated with the formation of flanged australites. This is also an enigma as cores typically lose 80% or more of their original mass whereas flanged buttons only lose approx. 50% of their mass.

Another peculiarity is that they can appear in very dense 'groups' but be totally absent in other areas. They are too fragile to have accumulated into these groups by erosional processes. Even Bill Cleverly came to the conclusion that they could not have moved more than a few metres from where they originally fell. The theory that they were far more common and that they have simply been eroded or dissolved away in most areas except in places where their preservation was ideal, also seems unjustified because I have found cores in a very good state of preservation clearly freshly eroding out of the "Wiluna Hard Pan' but not one mini tektite in some of these areas! From my own observations it seems that mini tektites fell in 'groups' and their creation and survival are due to unique conditions.

The examples below are taken from descriptions made by W.H.Cleverly of some well preserved types found in West Australia.

The following freehand drawings are not to scale but are for illustration purposes only. The top drawing in each square is the view from above and the bottom drawing is a longitudinal cross-section of it. Flight direction was towards the bottom of the page.

a. oval disc with thickened rim formed by overflow of melt glass from the anterior side. wt = 0.55 gms, 3.1 mm thick, 15.2 x 10.2mm

b. oval plate small with thickened rim but the thin, translucent centre has collapsed in flight resulting in a form which is concave towards the direction of flight. wt = 0.137 gms, 1.7mm thick, 9.0 x 6.7mm.

c. aberrant plate The remnants of the central primary body is long, curved and knobbly.. The greater part of the flange is at the wider end. It probably developed from an irregular primary shape which may have been curved and tapering but was rounded in cross-section. Such forms would not normally be aerodynamically stable and would be completely ablated away but an individual may become more stable with the rapid development of flange glass and survive. wt = 0.21 gms, 2.1mm thick, 15mm x 7.3mm.

d. shallow bowl This one had prominent flow ridges on the anterior side and some of the melt flowed over to form a wall on the posterior side. wt = 0.52 gms, 4.3mm thick, 11.4mm x 10.3mm.

e. pine - seed The flanges on the side are directed backwards but flatten out towards the ends. Most of the flange has been lost at one end but at the other end it has been folded back into contact with the posterior surface and partially fused with it. This folding back of the flange would have ended the stable oriented flight. wt = 0.5 gms, 4.2 thick, 18.2 x 9.9mm.

f. hollow form This is the eroded remnant of a hollow australite and consists of the flange and a portion of the posterior shell. The anterior shell may have collapsed due to the presence of a bubble cavity and been lost in flight or by later erosion.
wt = 0.39 gms, 12.5mm diameter.

g. narrow elongate plate One corner of the plate has been folded back onto the posterior surface and partially fused to it.
It is more likely that this folding happened in flight due to aerodynamic pressure while the speed was still high rather than by impact with the ground while still molten, as there are no soil grains imbedded in it. wt = 0.106 gms, 1.3mm thick, 16.0 x 5.4mm.

George Baker also made a study of disc, plate and bowl - shaped australites from the Port Cambell area. This area produced the most numerous and best developed forms in Australia. Baker notes that these forms are equally as rare in the well - developed state as flanged buttons.
33 specimens were recovered between 1934 and 1962 in the same area of 20 square miles near Port Cambell and they represented 1.5% of the total number of australites recovered in that area. 4 of the forms were sent to other institutions, but of the 29 remaining, George Baker made the following measurements :

	Number of specimens	Average weight (gms)	Average thickness of glass	Average length	Average overall width
Round discs with round core	7	0.211	1.0 mm	(9.0 mm diameter)	-
Oval discs with oval core	6	0.363	1.0 mm	12.5 mm	10.5mm
Oval discs with tear-shaped core	2	0.28	1.0 mm	10.25 mm	9.0 mm
Flat oval plates	2	0.194	0.75 mm	12.0 mm	10.0 mm
Round shallow bowls	2	0.214	1.0 mm	(9.0 mm diameter)	-
Oval shallow bowls	4	0.217	1.0 mm	10.0 mm	8.5 mm
Elongated deep bowls	4	0.196	0.75 mm	9.5 mm	6.0 mm
Elongated plate	1	0.277	1.0 mm	18.5 mm	8.5 mm
Aberrant plate	1	0.175	0.75 mm	12.5 mm	7.5 mm
Overall totals and averages	29	0.246	1.0 mm	11.0mm	8.5 mm

Conclusions

From these figures it can be seen that round discs are the most common form (24%)
Oval discs are the second most common form (21%)
The elongated or aberrant plates are the least common.
The thickness of these forms is consistantly close to 1.0 mm.
Round forms average 9.0 mm in diameter; oval and elongates average 11 mm x 8.5 mm.
The average specific gravity was 2.415 with little deviation.

If you look at the actual number of round or oval shapes it seems more likely that these originated from very small round or oval primary bodies that were possibly, but not necessarily, disc shaped and they represent the ultimate stage of ablation.

In conclusion it seems unlikely that a 'spalled' piece from a larger 'core' type tektite would have the time or velocity to have continued ablating long enough to have formed all these very thin rare shapes. However, I do think that flow melt lost from 'flanged' forms or lost flanges in flight may have resulted in many of these forms due to some of the unusual shapes found which are unlike types found from the classic primary bodies and also to the fact that they are more commonly found together with flanged tektites.

Their extreme rarity is no doubt due to their smallness and fragility making their survival on earth a rarity. Their smallness also making them extremely difficult to find.
The fact that any survive at all is incredible! But the fact that some have survived in such excellent condition and are found on the surface exposed to all the elements after an estimated 700,000 years is really beyond belief!

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I am calling this a 'barrel'! I found it only recently. It has small round flattened ends and flow lines between.

I still cannot imagine how this shape has formed! I have now found a few more small types known as the 'seed' type similar to this one but with pointed ends.

RARE AND UNUSUAL AUSTRALITE FORMS