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Round Cores
They start out as spheres. Some of the larger australites are round cores or
very close to being round (broad oval).
Out of 26 of the heaviest australites ever found, 20 were round cores or broad oval cores
ranging from 142 grams to the largest australite of 437 grams found near Notting in West
Australia. These together with the lenses, make up the bulk of most collections.
Lenses
These are the final stage of all australites and the most common form of all.
Most would be the remains of the round flanged buttons after the flange has been lost
either while still in flight or on impact with the ground, or through erosion.
They are biconvex with a sharp rim and many still have flow ridges on the anterior side
and a smooth posterior surface. In the Shaw collection they were four times as common as
other round forms.
Oval Cores
These formed from egg shaped primary bodies. Some smaller ones are the remains
of oval buttons that have lost their flange.
Of the 166 non flanged ovals, the sizes and weights in the Shaw collection were as
follows:
Length
Number Av.weight
18-21mm 18
2.01gms
14-18mm 50
1.22gms
10-14mm 81
0.64gms
8-10mm
17
0.214gms
It can be seen that ovals in the Shaw collection were very small, yet some very large oval cores have been found.
Boats
Boats are more elongate than ovals and have parallel sides but still rounded ends. Some of the smaller, thinner forms have traces of flanges and flow ridges which are often irregular and these forms seem to be most commonly found on the Lake Torrens Sand Plain. This group ranges in size from big to tiny. The occasional very large boat is found such as the 173.6 gm one found near Toolondo Victoria.
Left is boat with remnants of flange from Lake Torrens Plain, 6. 34 gms
(photo supplied by Guy Heinen).
The following figures come from the Shaw collection:
Length
Number Av.weight
20-30mm
15
2.24 gms
18-22mm
75
1.35 gms
14-18mm
52
0.53 gms
12-14mm
14
0.356 gms
8
0.321 gms (remarkably thin and translucent)
 |
A rare fully-flanged boat.
|
Canoes
These are similar to boats but they have pointed ends and are usually narrower. The pointed ends often turnaway from the direction of flight. In a small number there is a partial flange. They probably originate from an elongate with a rounded cross section .
A possible origin for the primary body could have been from a dumbell which became very elongated and finally broke in two place.
Left is a canoe with upturned ends from Lake Torrens Plain
1. 23 gms. (photo supplied by Guy Heinen)
The following figures come from the Shaw collection:
Length
Number
Av.weight
22-30mm
22
1.56 gms
18-22mm
18
1.18 gms
14-18mm
28
0.631 gms
12-14mm
7
0.452 gms
This form seems to be rare in some regions.
Dumbbells
The primary shapes were developed from elongated ovals when a fast rotation caused the two ends to pull apart to form a waist. The dumbbell australite core, however, has to keep a stable orientation with its greatest surface area presented forward in order for a perfect equatorial rim to develop. Many smaller thinner dumbbells show a partial flange. Some very large dumbbell cores have been found (176 gms at Cuballing W.A., 151 gms near Ongerup W.A.) . A few must enter the atmosphere tumbling as they do not form a rim.
Left is dumbbell australite showing ablation rim.
(Photo supplied by Guy Heinen)
The following figures come from the Shaw Collection:
Length
Number
Av.weight
30-35mm
5
2.648 gms
25-30mm
23
1.457 gms
20-25mm
25
0.860 gms
15-20mm
7
0.51 gms
There is another group of unusual dumbbells called 'ladles' in which one end is larger than the other and has orientated itself with the larger end forward. The flow lines extend up the handle. 5 were recorded in the Shaw collection.
Teardrops
When a dumbbell is torn completely apart it forms two teardrops. The pointed ends of a teardrop rarely survive the fall to earth or subsequent erosion. Many show a clear ablation rim despite the less than aerdynamically stable shape. In very rare cases the thinner forms may form a flange. There is a huge variety within this group from almost round (often big) to very elongated to very tiny and flanged.
Left is a tiny fragment of a teardrop with a flange on one side. It is so thin it is
partially translucent. 0. 7 gms, 15mm x 8mm
Some figures from the Shaw collection:
Short axis
Number
Av. weight
12-15mm
6
1.92 gms
10-12mm
21
1.23 gms
8-10mm
45
0.731 gms
6-8mm
39
0.417 gms
'air bombs'
23 - unusual misshaped forms which possibly tumbled through
the atmosphere
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